diff --git a/Lib/__future__.py b/Lib/__future__.py
new file mode 100644
index 000000000..63b2be352
--- /dev/null
+++ b/Lib/__future__.py
@@ -0,0 +1,140 @@
+"""Record of phased-in incompatible language changes.
+
+Each line is of the form:
+
+    FeatureName = "_Feature(" OptionalRelease "," MandatoryRelease ","
+                              CompilerFlag ")"
+
+where, normally, OptionalRelease < MandatoryRelease, and both are 5-tuples
+of the same form as sys.version_info:
+
+    (PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
+     PY_MINOR_VERSION, # the 1; an int
+     PY_MICRO_VERSION, # the 0; an int
+     PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
+     PY_RELEASE_SERIAL # the 3; an int
+    )
+
+OptionalRelease records the first release in which
+
+    from __future__ import FeatureName
+
+was accepted.
+
+In the case of MandatoryReleases that have not yet occurred,
+MandatoryRelease predicts the release in which the feature will become part
+of the language.
+
+Else MandatoryRelease records when the feature became part of the language;
+in releases at or after that, modules no longer need
+
+    from __future__ import FeatureName
+
+to use the feature in question, but may continue to use such imports.
+
+MandatoryRelease may also be None, meaning that a planned feature got
+dropped.
+
+Instances of class _Feature have two corresponding methods,
+.getOptionalRelease() and .getMandatoryRelease().
+
+CompilerFlag is the (bitfield) flag that should be passed in the fourth
+argument to the builtin function compile() to enable the feature in
+dynamically compiled code.  This flag is stored in the .compiler_flag
+attribute on _Future instances.  These values must match the appropriate
+#defines of CO_xxx flags in Include/compile.h.
+
+No feature line is ever to be deleted from this file.
+"""
+
+all_feature_names = [
+    "nested_scopes",
+    "generators",
+    "division",
+    "absolute_import",
+    "with_statement",
+    "print_function",
+    "unicode_literals",
+    "barry_as_FLUFL",
+    "generator_stop",
+]
+
+__all__ = ["all_feature_names"] + all_feature_names
+
+# The CO_xxx symbols are defined here under the same names used by
+# compile.h, so that an editor search will find them here.  However,
+# they're not exported in __all__, because they don't really belong to
+# this module.
+CO_NESTED            = 0x0010   # nested_scopes
+CO_GENERATOR_ALLOWED = 0        # generators (obsolete, was 0x1000)
+CO_FUTURE_DIVISION   = 0x2000   # division
+CO_FUTURE_ABSOLUTE_IMPORT = 0x4000 # perform absolute imports by default
+CO_FUTURE_WITH_STATEMENT  = 0x8000   # with statement
+CO_FUTURE_PRINT_FUNCTION  = 0x10000   # print function
+CO_FUTURE_UNICODE_LITERALS = 0x20000 # unicode string literals
+CO_FUTURE_BARRY_AS_BDFL = 0x40000
+CO_FUTURE_GENERATOR_STOP  = 0x80000 # StopIteration becomes RuntimeError in generators
+
+class _Feature:
+    def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
+        self.optional = optionalRelease
+        self.mandatory = mandatoryRelease
+        self.compiler_flag = compiler_flag
+
+    def getOptionalRelease(self):
+        """Return first release in which this feature was recognized.
+
+        This is a 5-tuple, of the same form as sys.version_info.
+        """
+
+        return self.optional
+
+    def getMandatoryRelease(self):
+        """Return release in which this feature will become mandatory.
+
+        This is a 5-tuple, of the same form as sys.version_info, or, if
+        the feature was dropped, is None.
+        """
+
+        return self.mandatory
+
+    def __repr__(self):
+        return "_Feature" + repr((self.optional,
+                                  self.mandatory,
+                                  self.compiler_flag))
+
+nested_scopes = _Feature((2, 1, 0, "beta",  1),
+                         (2, 2, 0, "alpha", 0),
+                         CO_NESTED)
+
+generators = _Feature((2, 2, 0, "alpha", 1),
+                      (2, 3, 0, "final", 0),
+                      CO_GENERATOR_ALLOWED)
+
+division = _Feature((2, 2, 0, "alpha", 2),
+                    (3, 0, 0, "alpha", 0),
+                    CO_FUTURE_DIVISION)
+
+absolute_import = _Feature((2, 5, 0, "alpha", 1),
+                           (3, 0, 0, "alpha", 0),
+                           CO_FUTURE_ABSOLUTE_IMPORT)
+
+with_statement = _Feature((2, 5, 0, "alpha", 1),
+                          (2, 6, 0, "alpha", 0),
+                          CO_FUTURE_WITH_STATEMENT)
+
+print_function = _Feature((2, 6, 0, "alpha", 2),
+                          (3, 0, 0, "alpha", 0),
+                          CO_FUTURE_PRINT_FUNCTION)
+
+unicode_literals = _Feature((2, 6, 0, "alpha", 2),
+                            (3, 0, 0, "alpha", 0),
+                            CO_FUTURE_UNICODE_LITERALS)
+
+barry_as_FLUFL = _Feature((3, 1, 0, "alpha", 2),
+                         (3, 9, 0, "alpha", 0),
+                         CO_FUTURE_BARRY_AS_BDFL)
+
+generator_stop = _Feature((3, 5, 0, "beta", 1),
+                         (3, 7, 0, "alpha", 0),
+                         CO_FUTURE_GENERATOR_STOP)
diff --git a/Lib/_compat_pickle.py b/Lib/_compat_pickle.py
new file mode 100644
index 000000000..f68496ae6
--- /dev/null
+++ b/Lib/_compat_pickle.py
@@ -0,0 +1,251 @@
+# This module is used to map the old Python 2 names to the new names used in
+# Python 3 for the pickle module.  This needed to make pickle streams
+# generated with Python 2 loadable by Python 3.
+
+# This is a copy of lib2to3.fixes.fix_imports.MAPPING.  We cannot import
+# lib2to3 and use the mapping defined there, because lib2to3 uses pickle.
+# Thus, this could cause the module to be imported recursively.
+IMPORT_MAPPING = {
+    '__builtin__' : 'builtins',
+    'copy_reg': 'copyreg',
+    'Queue': 'queue',
+    'SocketServer': 'socketserver',
+    'ConfigParser': 'configparser',
+    'repr': 'reprlib',
+    'tkFileDialog': 'tkinter.filedialog',
+    'tkSimpleDialog': 'tkinter.simpledialog',
+    'tkColorChooser': 'tkinter.colorchooser',
+    'tkCommonDialog': 'tkinter.commondialog',
+    'Dialog': 'tkinter.dialog',
+    'Tkdnd': 'tkinter.dnd',
+    'tkFont': 'tkinter.font',
+    'tkMessageBox': 'tkinter.messagebox',
+    'ScrolledText': 'tkinter.scrolledtext',
+    'Tkconstants': 'tkinter.constants',
+    'Tix': 'tkinter.tix',
+    'ttk': 'tkinter.ttk',
+    'Tkinter': 'tkinter',
+    'markupbase': '_markupbase',
+    '_winreg': 'winreg',
+    'thread': '_thread',
+    'dummy_thread': '_dummy_thread',
+    'dbhash': 'dbm.bsd',
+    'dumbdbm': 'dbm.dumb',
+    'dbm': 'dbm.ndbm',
+    'gdbm': 'dbm.gnu',
+    'xmlrpclib': 'xmlrpc.client',
+    'SimpleXMLRPCServer': 'xmlrpc.server',
+    'httplib': 'http.client',
+    'htmlentitydefs' : 'html.entities',
+    'HTMLParser' : 'html.parser',
+    'Cookie': 'http.cookies',
+    'cookielib': 'http.cookiejar',
+    'BaseHTTPServer': 'http.server',
+    'test.test_support': 'test.support',
+    'commands': 'subprocess',
+    'urlparse' : 'urllib.parse',
+    'robotparser' : 'urllib.robotparser',
+    'urllib2': 'urllib.request',
+    'anydbm': 'dbm',
+    '_abcoll' : 'collections.abc',
+}
+
+
+# This contains rename rules that are easy to handle.  We ignore the more
+# complex stuff (e.g. mapping the names in the urllib and types modules).
+# These rules should be run before import names are fixed.
+NAME_MAPPING = {
+    ('__builtin__', 'xrange'):     ('builtins', 'range'),
+    ('__builtin__', 'reduce'):     ('functools', 'reduce'),
+    ('__builtin__', 'intern'):     ('sys', 'intern'),
+    ('__builtin__', 'unichr'):     ('builtins', 'chr'),
+    ('__builtin__', 'unicode'):    ('builtins', 'str'),
+    ('__builtin__', 'long'):       ('builtins', 'int'),
+    ('itertools', 'izip'):         ('builtins', 'zip'),
+    ('itertools', 'imap'):         ('builtins', 'map'),
+    ('itertools', 'ifilter'):      ('builtins', 'filter'),
+    ('itertools', 'ifilterfalse'): ('itertools', 'filterfalse'),
+    ('itertools', 'izip_longest'): ('itertools', 'zip_longest'),
+    ('UserDict', 'IterableUserDict'): ('collections', 'UserDict'),
+    ('UserList', 'UserList'): ('collections', 'UserList'),
+    ('UserString', 'UserString'): ('collections', 'UserString'),
+    ('whichdb', 'whichdb'): ('dbm', 'whichdb'),
+    ('_socket', 'fromfd'): ('socket', 'fromfd'),
+    ('_multiprocessing', 'Connection'): ('multiprocessing.connection', 'Connection'),
+    ('multiprocessing.process', 'Process'): ('multiprocessing.context', 'Process'),
+    ('multiprocessing.forking', 'Popen'): ('multiprocessing.popen_fork', 'Popen'),
+    ('urllib', 'ContentTooShortError'): ('urllib.error', 'ContentTooShortError'),
+    ('urllib', 'getproxies'): ('urllib.request', 'getproxies'),
+    ('urllib', 'pathname2url'): ('urllib.request', 'pathname2url'),
+    ('urllib', 'quote_plus'): ('urllib.parse', 'quote_plus'),
+    ('urllib', 'quote'): ('urllib.parse', 'quote'),
+    ('urllib', 'unquote_plus'): ('urllib.parse', 'unquote_plus'),
+    ('urllib', 'unquote'): ('urllib.parse', 'unquote'),
+    ('urllib', 'url2pathname'): ('urllib.request', 'url2pathname'),
+    ('urllib', 'urlcleanup'): ('urllib.request', 'urlcleanup'),
+    ('urllib', 'urlencode'): ('urllib.parse', 'urlencode'),
+    ('urllib', 'urlopen'): ('urllib.request', 'urlopen'),
+    ('urllib', 'urlretrieve'): ('urllib.request', 'urlretrieve'),
+    ('urllib2', 'HTTPError'): ('urllib.error', 'HTTPError'),
+    ('urllib2', 'URLError'): ('urllib.error', 'URLError'),
+}
+
+PYTHON2_EXCEPTIONS = (
+    "ArithmeticError",
+    "AssertionError",
+    "AttributeError",
+    "BaseException",
+    "BufferError",
+    "BytesWarning",
+    "DeprecationWarning",
+    "EOFError",
+    "EnvironmentError",
+    "Exception",
+    "FloatingPointError",
+    "FutureWarning",
+    "GeneratorExit",
+    "IOError",
+    "ImportError",
+    "ImportWarning",
+    "IndentationError",
+    "IndexError",
+    "KeyError",
+    "KeyboardInterrupt",
+    "LookupError",
+    "MemoryError",
+    "NameError",
+    "NotImplementedError",
+    "OSError",
+    "OverflowError",
+    "PendingDeprecationWarning",
+    "ReferenceError",
+    "RuntimeError",
+    "RuntimeWarning",
+    # StandardError is gone in Python 3, so we map it to Exception
+    "StopIteration",
+    "SyntaxError",
+    "SyntaxWarning",
+    "SystemError",
+    "SystemExit",
+    "TabError",
+    "TypeError",
+    "UnboundLocalError",
+    "UnicodeDecodeError",
+    "UnicodeEncodeError",
+    "UnicodeError",
+    "UnicodeTranslateError",
+    "UnicodeWarning",
+    "UserWarning",
+    "ValueError",
+    "Warning",
+    "ZeroDivisionError",
+)
+
+try:
+    WindowsError
+except NameError:
+    pass
+else:
+    PYTHON2_EXCEPTIONS += ("WindowsError",)
+
+for excname in PYTHON2_EXCEPTIONS:
+    NAME_MAPPING[("exceptions", excname)] = ("builtins", excname)
+
+MULTIPROCESSING_EXCEPTIONS = (
+    'AuthenticationError',
+    'BufferTooShort',
+    'ProcessError',
+    'TimeoutError',
+)
+
+for excname in MULTIPROCESSING_EXCEPTIONS:
+    NAME_MAPPING[("multiprocessing", excname)] = ("multiprocessing.context", excname)
+
+# Same, but for 3.x to 2.x
+REVERSE_IMPORT_MAPPING = dict((v, k) for (k, v) in IMPORT_MAPPING.items())
+assert len(REVERSE_IMPORT_MAPPING) == len(IMPORT_MAPPING)
+REVERSE_NAME_MAPPING = dict((v, k) for (k, v) in NAME_MAPPING.items())
+assert len(REVERSE_NAME_MAPPING) == len(NAME_MAPPING)
+
+# Non-mutual mappings.
+
+IMPORT_MAPPING.update({
+    'cPickle': 'pickle',
+    '_elementtree': 'xml.etree.ElementTree',
+    'FileDialog': 'tkinter.filedialog',
+    'SimpleDialog': 'tkinter.simpledialog',
+    'DocXMLRPCServer': 'xmlrpc.server',
+    'SimpleHTTPServer': 'http.server',
+    'CGIHTTPServer': 'http.server',
+    # For compatibility with broken pickles saved in old Python 3 versions
+    'UserDict': 'collections',
+    'UserList': 'collections',
+    'UserString': 'collections',
+    'whichdb': 'dbm',
+    'StringIO':  'io',
+    'cStringIO': 'io',
+})
+
+REVERSE_IMPORT_MAPPING.update({
+    '_bz2': 'bz2',
+    '_dbm': 'dbm',
+    '_functools': 'functools',
+    '_gdbm': 'gdbm',
+    '_pickle': 'pickle',
+})
+
+NAME_MAPPING.update({
+    ('__builtin__', 'basestring'): ('builtins', 'str'),
+    ('exceptions', 'StandardError'): ('builtins', 'Exception'),
+    ('UserDict', 'UserDict'): ('collections', 'UserDict'),
+    ('socket', '_socketobject'): ('socket', 'SocketType'),
+})
+
+REVERSE_NAME_MAPPING.update({
+    ('_functools', 'reduce'): ('__builtin__', 'reduce'),
+    ('tkinter.filedialog', 'FileDialog'): ('FileDialog', 'FileDialog'),
+    ('tkinter.filedialog', 'LoadFileDialog'): ('FileDialog', 'LoadFileDialog'),
+    ('tkinter.filedialog', 'SaveFileDialog'): ('FileDialog', 'SaveFileDialog'),
+    ('tkinter.simpledialog', 'SimpleDialog'): ('SimpleDialog', 'SimpleDialog'),
+    ('xmlrpc.server', 'ServerHTMLDoc'): ('DocXMLRPCServer', 'ServerHTMLDoc'),
+    ('xmlrpc.server', 'XMLRPCDocGenerator'):
+        ('DocXMLRPCServer', 'XMLRPCDocGenerator'),
+    ('xmlrpc.server', 'DocXMLRPCRequestHandler'):
+        ('DocXMLRPCServer', 'DocXMLRPCRequestHandler'),
+    ('xmlrpc.server', 'DocXMLRPCServer'):
+        ('DocXMLRPCServer', 'DocXMLRPCServer'),
+    ('xmlrpc.server', 'DocCGIXMLRPCRequestHandler'):
+        ('DocXMLRPCServer', 'DocCGIXMLRPCRequestHandler'),
+    ('http.server', 'SimpleHTTPRequestHandler'):
+        ('SimpleHTTPServer', 'SimpleHTTPRequestHandler'),
+    ('http.server', 'CGIHTTPRequestHandler'):
+        ('CGIHTTPServer', 'CGIHTTPRequestHandler'),
+    ('_socket', 'socket'): ('socket', '_socketobject'),
+})
+
+PYTHON3_OSERROR_EXCEPTIONS = (
+    'BrokenPipeError',
+    'ChildProcessError',
+    'ConnectionAbortedError',
+    'ConnectionError',
+    'ConnectionRefusedError',
+    'ConnectionResetError',
+    'FileExistsError',
+    'FileNotFoundError',
+    'InterruptedError',
+    'IsADirectoryError',
+    'NotADirectoryError',
+    'PermissionError',
+    'ProcessLookupError',
+    'TimeoutError',
+)
+
+for excname in PYTHON3_OSERROR_EXCEPTIONS:
+    REVERSE_NAME_MAPPING[('builtins', excname)] = ('exceptions', 'OSError')
+
+PYTHON3_IMPORTERROR_EXCEPTIONS = (
+    'ModuleNotFoundError',
+)
+
+for excname in PYTHON3_IMPORTERROR_EXCEPTIONS:
+    REVERSE_NAME_MAPPING[('builtins', excname)] = ('exceptions', 'ImportError')
diff --git a/Lib/_dummy_thread.py b/Lib/_dummy_thread.py
new file mode 100644
index 000000000..36e5f38ae
--- /dev/null
+++ b/Lib/_dummy_thread.py
@@ -0,0 +1,163 @@
+"""Drop-in replacement for the thread module.
+
+Meant to be used as a brain-dead substitute so that threaded code does
+not need to be rewritten for when the thread module is not present.
+
+Suggested usage is::
+
+    try:
+        import _thread
+    except ImportError:
+        import _dummy_thread as _thread
+
+"""
+# Exports only things specified by thread documentation;
+# skipping obsolete synonyms allocate(), start_new(), exit_thread().
+__all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
+           'interrupt_main', 'LockType']
+
+# A dummy value
+TIMEOUT_MAX = 2**31
+
+# NOTE: this module can be imported early in the extension building process,
+# and so top level imports of other modules should be avoided.  Instead, all
+# imports are done when needed on a function-by-function basis.  Since threads
+# are disabled, the import lock should not be an issue anyway (??).
+
+error = RuntimeError
+
+def start_new_thread(function, args, kwargs={}):
+    """Dummy implementation of _thread.start_new_thread().
+
+    Compatibility is maintained by making sure that ``args`` is a
+    tuple and ``kwargs`` is a dictionary.  If an exception is raised
+    and it is SystemExit (which can be done by _thread.exit()) it is
+    caught and nothing is done; all other exceptions are printed out
+    by using traceback.print_exc().
+
+    If the executed function calls interrupt_main the KeyboardInterrupt will be
+    raised when the function returns.
+
+    """
+    if type(args) != type(tuple()):
+        raise TypeError("2nd arg must be a tuple")
+    if type(kwargs) != type(dict()):
+        raise TypeError("3rd arg must be a dict")
+    global _main
+    _main = False
+    try:
+        function(*args, **kwargs)
+    except SystemExit:
+        pass
+    except:
+        import traceback
+        traceback.print_exc()
+    _main = True
+    global _interrupt
+    if _interrupt:
+        _interrupt = False
+        raise KeyboardInterrupt
+
+def exit():
+    """Dummy implementation of _thread.exit()."""
+    raise SystemExit
+
+def get_ident():
+    """Dummy implementation of _thread.get_ident().
+
+    Since this module should only be used when _threadmodule is not
+    available, it is safe to assume that the current process is the
+    only thread.  Thus a constant can be safely returned.
+    """
+    return -1
+
+def allocate_lock():
+    """Dummy implementation of _thread.allocate_lock()."""
+    return LockType()
+
+def stack_size(size=None):
+    """Dummy implementation of _thread.stack_size()."""
+    if size is not None:
+        raise error("setting thread stack size not supported")
+    return 0
+
+def _set_sentinel():
+    """Dummy implementation of _thread._set_sentinel()."""
+    return LockType()
+
+class LockType(object):
+    """Class implementing dummy implementation of _thread.LockType.
+
+    Compatibility is maintained by maintaining self.locked_status
+    which is a boolean that stores the state of the lock.  Pickling of
+    the lock, though, should not be done since if the _thread module is
+    then used with an unpickled ``lock()`` from here problems could
+    occur from this class not having atomic methods.
+
+    """
+
+    def __init__(self):
+        self.locked_status = False
+
+    def acquire(self, waitflag=None, timeout=-1):
+        """Dummy implementation of acquire().
+
+        For blocking calls, self.locked_status is automatically set to
+        True and returned appropriately based on value of
+        ``waitflag``.  If it is non-blocking, then the value is
+        actually checked and not set if it is already acquired.  This
+        is all done so that threading.Condition's assert statements
+        aren't triggered and throw a little fit.
+
+        """
+        if waitflag is None or waitflag:
+            self.locked_status = True
+            return True
+        else:
+            if not self.locked_status:
+                self.locked_status = True
+                return True
+            else:
+                if timeout > 0:
+                    import time
+                    time.sleep(timeout)
+                return False
+
+    __enter__ = acquire
+
+    def __exit__(self, typ, val, tb):
+        self.release()
+
+    def release(self):
+        """Release the dummy lock."""
+        # XXX Perhaps shouldn't actually bother to test?  Could lead
+        #     to problems for complex, threaded code.
+        if not self.locked_status:
+            raise error
+        self.locked_status = False
+        return True
+
+    def locked(self):
+        return self.locked_status
+
+    def __repr__(self):
+        return "<%s %s.%s object at %s>" % (
+            "locked" if self.locked_status else "unlocked",
+            self.__class__.__module__,
+            self.__class__.__qualname__,
+            hex(id(self))
+        )
+
+# Used to signal that interrupt_main was called in a "thread"
+_interrupt = False
+# True when not executing in a "thread"
+_main = True
+
+def interrupt_main():
+    """Set _interrupt flag to True to have start_new_thread raise
+    KeyboardInterrupt upon exiting."""
+    if _main:
+        raise KeyboardInterrupt
+    else:
+        global _interrupt
+        _interrupt = True
diff --git a/Lib/_markupbase.py b/Lib/_markupbase.py
new file mode 100644
index 000000000..2af5f1c23
--- /dev/null
+++ b/Lib/_markupbase.py
@@ -0,0 +1,395 @@
+"""Shared support for scanning document type declarations in HTML and XHTML.
+
+This module is used as a foundation for the html.parser module.  It has no
+documented public API and should not be used directly.
+
+"""
+
+import re
+
+_declname_match = re.compile(r'[a-zA-Z][-_.a-zA-Z0-9]*\s*').match
+_declstringlit_match = re.compile(r'(\'[^\']*\'|"[^"]*")\s*').match
+_commentclose = re.compile(r'--\s*>')
+_markedsectionclose = re.compile(r']\s*]\s*>')
+
+# An analysis of the MS-Word extensions is available at
+# http://www.planetpublish.com/xmlarena/xap/Thursday/WordtoXML.pdf
+
+_msmarkedsectionclose = re.compile(r']\s*>')
+
+del re
+
+
+class ParserBase:
+    """Parser base class which provides some common support methods used
+    by the SGML/HTML and XHTML parsers."""
+
+    def __init__(self):
+        if self.__class__ is ParserBase:
+            raise RuntimeError(
+                "_markupbase.ParserBase must be subclassed")
+
+    def error(self, message):
+        raise NotImplementedError(
+            "subclasses of ParserBase must override error()")
+
+    def reset(self):
+        self.lineno = 1
+        self.offset = 0
+
+    def getpos(self):
+        """Return current line number and offset."""
+        return self.lineno, self.offset
+
+    # Internal -- update line number and offset.  This should be
+    # called for each piece of data exactly once, in order -- in other
+    # words the concatenation of all the input strings to this
+    # function should be exactly the entire input.
+    def updatepos(self, i, j):
+        if i >= j:
+            return j
+        rawdata = self.rawdata
+        nlines = rawdata.count("\n", i, j)
+        if nlines:
+            self.lineno = self.lineno + nlines
+            pos = rawdata.rindex("\n", i, j) # Should not fail
+            self.offset = j-(pos+1)
+        else:
+            self.offset = self.offset + j-i
+        return j
+
+    _decl_otherchars = ''
+
+    # Internal -- parse declaration (for use by subclasses).
+    def parse_declaration(self, i):
+        # This is some sort of declaration; in "HTML as
+        # deployed," this should only be the document type
+        # declaration ("<!DOCTYPE html...>").
+        # ISO 8879:1986, however, has more complex
+        # declaration syntax for elements in <!...>, including:
+        # --comment--
+        # [marked section]
+        # name in the following list: ENTITY, DOCTYPE, ELEMENT,
+        # ATTLIST, NOTATION, SHORTREF, USEMAP,
+        # LINKTYPE, LINK, IDLINK, USELINK, SYSTEM
+        rawdata = self.rawdata
+        j = i + 2
+        assert rawdata[i:j] == "<!", "unexpected call to parse_declaration"
+        if rawdata[j:j+1] == ">":
+            # the empty comment <!>
+            return j + 1
+        if rawdata[j:j+1] in ("-", ""):
+            # Start of comment followed by buffer boundary,
+            # or just a buffer boundary.
+            return -1
+        # A simple, practical version could look like: ((name|stringlit) S*) + '>'
+        n = len(rawdata)
+        if rawdata[j:j+2] == '--': #comment
+            # Locate --.*-- as the body of the comment
+            return self.parse_comment(i)
+        elif rawdata[j] == '[': #marked section
+            # Locate [statusWord [...arbitrary SGML...]] as the body of the marked section
+            # Where statusWord is one of TEMP, CDATA, IGNORE, INCLUDE, RCDATA
+            # Note that this is extended by Microsoft Office "Save as Web" function
+            # to include [if...] and [endif].
+            return self.parse_marked_section(i)
+        else: #all other declaration elements
+            decltype, j = self._scan_name(j, i)
+        if j < 0:
+            return j
+        if decltype == "doctype":
+            self._decl_otherchars = ''
+        while j < n:
+            c = rawdata[j]
+            if c == ">":
+                # end of declaration syntax
+                data = rawdata[i+2:j]
+                if decltype == "doctype":
+                    self.handle_decl(data)
+                else:
+                    # According to the HTML5 specs sections "8.2.4.44 Bogus
+                    # comment state" and "8.2.4.45 Markup declaration open
+                    # state", a comment token should be emitted.
+                    # Calling unknown_decl provides more flexibility though.
+                    self.unknown_decl(data)
+                return j + 1
+            if c in "\"'":
+                m = _declstringlit_match(rawdata, j)
+                if not m:
+                    return -1 # incomplete
+                j = m.end()
+            elif c in "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ":
+                name, j = self._scan_name(j, i)
+            elif c in self._decl_otherchars:
+                j = j + 1
+            elif c == "[":
+                # this could be handled in a separate doctype parser
+                if decltype == "doctype":
+                    j = self._parse_doctype_subset(j + 1, i)
+                elif decltype in {"attlist", "linktype", "link", "element"}:
+                    # must tolerate []'d groups in a content model in an element declaration
+                    # also in data attribute specifications of attlist declaration
+                    # also link type declaration subsets in linktype declarations
+                    # also link attribute specification lists in link declarations
+                    self.error("unsupported '[' char in %s declaration" % decltype)
+                else:
+                    self.error("unexpected '[' char in declaration")
+            else:
+                self.error(
+                    "unexpected %r char in declaration" % rawdata[j])
+            if j < 0:
+                return j
+        return -1 # incomplete
+
+    # Internal -- parse a marked section
+    # Override this to handle MS-word extension syntax <![if word]>content<![endif]>
+    def parse_marked_section(self, i, report=1):
+        rawdata= self.rawdata
+        assert rawdata[i:i+3] == '<![', "unexpected call to parse_marked_section()"
+        sectName, j = self._scan_name( i+3, i )
+        if j < 0:
+            return j
+        if sectName in {"temp", "cdata", "ignore", "include", "rcdata"}:
+            # look for standard ]]> ending
+            match= _markedsectionclose.search(rawdata, i+3)
+        elif sectName in {"if", "else", "endif"}:
+            # look for MS Office ]> ending
+            match= _msmarkedsectionclose.search(rawdata, i+3)
+        else:
+            self.error('unknown status keyword %r in marked section' % rawdata[i+3:j])
+        if not match:
+            return -1
+        if report:
+            j = match.start(0)
+            self.unknown_decl(rawdata[i+3: j])
+        return match.end(0)
+
+    # Internal -- parse comment, return length or -1 if not terminated
+    def parse_comment(self, i, report=1):
+        rawdata = self.rawdata
+        if rawdata[i:i+4] != '<!--':
+            self.error('unexpected call to parse_comment()')
+        match = _commentclose.search(rawdata, i+4)
+        if not match:
+            return -1
+        if report:
+            j = match.start(0)
+            self.handle_comment(rawdata[i+4: j])
+        return match.end(0)
+
+    # Internal -- scan past the internal subset in a <!DOCTYPE declaration,
+    # returning the index just past any whitespace following the trailing ']'.
+    def _parse_doctype_subset(self, i, declstartpos):
+        rawdata = self.rawdata
+        n = len(rawdata)
+        j = i
+        while j < n:
+            c = rawdata[j]
+            if c == "<":
+                s = rawdata[j:j+2]
+                if s == "<":
+                    # end of buffer; incomplete
+                    return -1
+                if s != "<!":
+                    self.updatepos(declstartpos, j + 1)
+                    self.error("unexpected char in internal subset (in %r)" % s)
+                if (j + 2) == n:
+                    # end of buffer; incomplete
+                    return -1
+                if (j + 4) > n:
+                    # end of buffer; incomplete
+                    return -1
+                if rawdata[j:j+4] == "<!--":
+                    j = self.parse_comment(j, report=0)
+                    if j < 0:
+                        return j
+                    continue
+                name, j = self._scan_name(j + 2, declstartpos)
+                if j == -1:
+                    return -1
+                if name not in {"attlist", "element", "entity", "notation"}:
+                    self.updatepos(declstartpos, j + 2)
+                    self.error(
+                        "unknown declaration %r in internal subset" % name)
+                # handle the individual names
+                meth = getattr(self, "_parse_doctype_" + name)
+                j = meth(j, declstartpos)
+                if j < 0:
+                    return j
+            elif c == "%":
+                # parameter entity reference
+                if (j + 1) == n:
+                    # end of buffer; incomplete
+                    return -1
+                s, j = self._scan_name(j + 1, declstartpos)
+                if j < 0:
+                    return j
+                if rawdata[j] == ";":
+                    j = j + 1
+            elif c == "]":
+                j = j + 1
+                while j < n and rawdata[j].isspace():
+                    j = j + 1
+                if j < n:
+                    if rawdata[j] == ">":
+                        return j
+                    self.updatepos(declstartpos, j)
+                    self.error("unexpected char after internal subset")
+                else:
+                    return -1
+            elif c.isspace():
+                j = j + 1
+            else:
+                self.updatepos(declstartpos, j)
+                self.error("unexpected char %r in internal subset" % c)
+        # end of buffer reached
+        return -1
+
+    # Internal -- scan past <!ELEMENT declarations
+    def _parse_doctype_element(self, i, declstartpos):
+        name, j = self._scan_name(i, declstartpos)
+        if j == -1:
+            return -1
+        # style content model; just skip until '>'
+        rawdata = self.rawdata
+        if '>' in rawdata[j:]:
+            return rawdata.find(">", j) + 1
+        return -1
+
+    # Internal -- scan past <!ATTLIST declarations
+    def _parse_doctype_attlist(self, i, declstartpos):
+        rawdata = self.rawdata
+        name, j = self._scan_name(i, declstartpos)
+        c = rawdata[j:j+1]
+        if c == "":
+            return -1
+        if c == ">":
+            return j + 1
+        while 1:
+            # scan a series of attribute descriptions; simplified:
+            #   name type [value] [#constraint]
+            name, j = self._scan_name(j, declstartpos)
+            if j < 0:
+                return j
+            c = rawdata[j:j+1]
+            if c == "":
+                return -1
+            if c == "(":
+                # an enumerated type; look for ')'
+                if ")" in rawdata[j:]:
+                    j = rawdata.find(")", j) + 1
+                else:
+                    return -1
+                while rawdata[j:j+1].isspace():
+                    j = j + 1
+                if not rawdata[j:]:
+                    # end of buffer, incomplete
+                    return -1
+            else:
+                name, j = self._scan_name(j, declstartpos)
+            c = rawdata[j:j+1]
+            if not c:
+                return -1
+            if c in "'\"":
+                m = _declstringlit_match(rawdata, j)
+                if m:
+                    j = m.end()
+                else:
+                    return -1
+                c = rawdata[j:j+1]
+                if not c:
+                    return -1
+            if c == "#":
+                if rawdata[j:] == "#":
+                    # end of buffer
+                    return -1
+                name, j = self._scan_name(j + 1, declstartpos)
+                if j < 0:
+                    return j
+                c = rawdata[j:j+1]
+                if not c:
+                    return -1
+            if c == '>':
+                # all done
+                return j + 1
+
+    # Internal -- scan past <!NOTATION declarations
+    def _parse_doctype_notation(self, i, declstartpos):
+        name, j = self._scan_name(i, declstartpos)
+        if j < 0:
+            return j
+        rawdata = self.rawdata
+        while 1:
+            c = rawdata[j:j+1]
+            if not c:
+                # end of buffer; incomplete
+                return -1
+            if c == '>':
+                return j + 1
+            if c in "'\"":
+                m = _declstringlit_match(rawdata, j)
+                if not m:
+                    return -1
+                j = m.end()
+            else:
+                name, j = self._scan_name(j, declstartpos)
+                if j < 0:
+                    return j
+
+    # Internal -- scan past <!ENTITY declarations
+    def _parse_doctype_entity(self, i, declstartpos):
+        rawdata = self.rawdata
+        if rawdata[i:i+1] == "%":
+            j = i + 1
+            while 1:
+                c = rawdata[j:j+1]
+                if not c:
+                    return -1
+                if c.isspace():
+                    j = j + 1
+                else:
+                    break
+        else:
+            j = i
+        name, j = self._scan_name(j, declstartpos)
+        if j < 0:
+            return j
+        while 1:
+            c = self.rawdata[j:j+1]
+            if not c:
+                return -1
+            if c in "'\"":
+                m = _declstringlit_match(rawdata, j)
+                if m:
+                    j = m.end()
+                else:
+                    return -1    # incomplete
+            elif c == ">":
+                return j + 1
+            else:
+                name, j = self._scan_name(j, declstartpos)
+                if j < 0:
+                    return j
+
+    # Internal -- scan a name token and the new position and the token, or
+    # return -1 if we've reached the end of the buffer.
+    def _scan_name(self, i, declstartpos):
+        rawdata = self.rawdata
+        n = len(rawdata)
+        if i == n:
+            return None, -1
+        m = _declname_match(rawdata, i)
+        if m:
+            s = m.group()
+            name = s.strip()
+            if (i + len(s)) == n:
+                return None, -1  # end of buffer
+            return name.lower(), m.end()
+        else:
+            self.updatepos(declstartpos, i)
+            self.error("expected name token at %r"
+                       % rawdata[declstartpos:declstartpos+20])
+
+    # To be overridden -- handlers for unknown objects
+    def unknown_decl(self, data):
+        pass
diff --git a/Lib/_sitebuiltins.py b/Lib/_sitebuiltins.py
new file mode 100644
index 000000000..c29cf4bf8
--- /dev/null
+++ b/Lib/_sitebuiltins.py
@@ -0,0 +1,103 @@
+"""
+The objects used by the site module to add custom builtins.
+"""
+
+# Those objects are almost immortal and they keep a reference to their module
+# globals.  Defining them in the site module would keep too many references
+# alive.
+# Note this means this module should also avoid keep things alive in its
+# globals.
+
+import sys
+
+class Quitter(object):
+    def __init__(self, name, eof):
+        self.name = name
+        self.eof = eof
+    def __repr__(self):
+        return 'Use %s() or %s to exit' % (self.name, self.eof)
+    def __call__(self, code=None):
+        # Shells like IDLE catch the SystemExit, but listen when their
+        # stdin wrapper is closed.
+        try:
+            sys.stdin.close()
+        except:
+            pass
+        raise SystemExit(code)
+
+
+class _Printer(object):
+    """interactive prompt objects for printing the license text, a list of
+    contributors and the copyright notice."""
+
+    MAXLINES = 23
+
+    def __init__(self, name, data, files=(), dirs=()):
+        import os
+        self.__name = name
+        self.__data = data
+        self.__lines = None
+        self.__filenames = [os.path.join(dir, filename)
+                            for dir in dirs
+                            for filename in files]
+
+    def __setup(self):
+        if self.__lines:
+            return
+        data = None
+        for filename in self.__filenames:
+            try:
+                with open(filename, "r") as fp:
+                    data = fp.read()
+                break
+            except OSError:
+                pass
+        if not data:
+            data = self.__data
+        self.__lines = data.split('\n')
+        self.__linecnt = len(self.__lines)
+
+    def __repr__(self):
+        self.__setup()
+        if len(self.__lines) <= self.MAXLINES:
+            return "\n".join(self.__lines)
+        else:
+            return "Type %s() to see the full %s text" % ((self.__name,)*2)
+
+    def __call__(self):
+        self.__setup()
+        prompt = 'Hit Return for more, or q (and Return) to quit: '
+        lineno = 0
+        while 1:
+            try:
+                for i in range(lineno, lineno + self.MAXLINES):
+                    print(self.__lines[i])
+            except IndexError:
+                break
+            else:
+                lineno += self.MAXLINES
+                key = None
+                while key is None:
+                    key = input(prompt)
+                    if key not in ('', 'q'):
+                        key = None
+                if key == 'q':
+                    break
+
+
+class _Helper(object):
+    """Define the builtin 'help'.
+
+    This is a wrapper around pydoc.help that provides a helpful message
+    when 'help' is typed at the Python interactive prompt.
+
+    Calling help() at the Python prompt starts an interactive help session.
+    Calling help(thing) prints help for the python object 'thing'.
+    """
+
+    def __repr__(self):
+        return "Type help() for interactive help, " \
+               "or help(object) for help about object."
+    def __call__(self, *args, **kwds):
+        import pydoc
+        return pydoc.help(*args, **kwds)
diff --git a/Lib/base64.py b/Lib/base64.py
new file mode 100755
index 000000000..c4313c33f
--- /dev/null
+++ b/Lib/base64.py
@@ -0,0 +1,595 @@
+#! /usr/bin/python3.6
+
+"""Base16, Base32, Base64 (RFC 3548), Base85 and Ascii85 data encodings"""
+
+# Modified 04-Oct-1995 by Jack Jansen to use binascii module
+# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
+# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
+
+import re
+import struct
+import binascii
+
+
+__all__ = [
+    # Legacy interface exports traditional RFC 2045 Base64 encodings
+    'encode', 'decode', 'encodebytes', 'decodebytes',
+    # Generalized interface for other encodings
+    'b64encode', 'b64decode', 'b32encode', 'b32decode',
+    'b16encode', 'b16decode',
+    # Base85 and Ascii85 encodings
+    'b85encode', 'b85decode', 'a85encode', 'a85decode',
+    # Standard Base64 encoding
+    'standard_b64encode', 'standard_b64decode',
+    # Some common Base64 alternatives.  As referenced by RFC 3458, see thread
+    # starting at:
+    #
+    # http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html
+    'urlsafe_b64encode', 'urlsafe_b64decode',
+    ]
+
+
+bytes_types = (bytes, bytearray)  # Types acceptable as binary data
+
+def _bytes_from_decode_data(s):
+    if isinstance(s, str):
+        try:
+            return s.encode('ascii')
+        except UnicodeEncodeError:
+            raise ValueError('string argument should contain only ASCII characters')
+    if isinstance(s, bytes_types):
+        return s
+    try:
+        return memoryview(s).tobytes()
+    except TypeError:
+        raise TypeError("argument should be a bytes-like object or ASCII "
+                        "string, not %r" % s.__class__.__name__) from None
+
+
+# Base64 encoding/decoding uses binascii
+
+def b64encode(s, altchars=None):
+    """Encode the bytes-like object s using Base64 and return a bytes object.
+
+    Optional altchars should be a byte string of length 2 which specifies an
+    alternative alphabet for the '+' and '/' characters.  This allows an
+    application to e.g. generate url or filesystem safe Base64 strings.
+    """
+    encoded = binascii.b2a_base64(s, newline=False)
+    if altchars is not None:
+        assert len(altchars) == 2, repr(altchars)
+        return encoded.translate(bytes.maketrans(b'+/', altchars))
+    return encoded
+
+
+def b64decode(s, altchars=None, validate=False):
+    """Decode the Base64 encoded bytes-like object or ASCII string s.
+
+    Optional altchars must be a bytes-like object or ASCII string of length 2
+    which specifies the alternative alphabet used instead of the '+' and '/'
+    characters.
+
+    The result is returned as a bytes object.  A binascii.Error is raised if
+    s is incorrectly padded.
+
+    If validate is False (the default), characters that are neither in the
+    normal base-64 alphabet nor the alternative alphabet are discarded prior
+    to the padding check.  If validate is True, these non-alphabet characters
+    in the input result in a binascii.Error.
+    """
+    s = _bytes_from_decode_data(s)
+    if altchars is not None:
+        altchars = _bytes_from_decode_data(altchars)
+        assert len(altchars) == 2, repr(altchars)
+        s = s.translate(bytes.maketrans(altchars, b'+/'))
+    if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
+        raise binascii.Error('Non-base64 digit found')
+    return binascii.a2b_base64(s)
+
+
+def standard_b64encode(s):
+    """Encode bytes-like object s using the standard Base64 alphabet.
+
+    The result is returned as a bytes object.
+    """
+    return b64encode(s)
+
+def standard_b64decode(s):
+    """Decode bytes encoded with the standard Base64 alphabet.
+
+    Argument s is a bytes-like object or ASCII string to decode.  The result
+    is returned as a bytes object.  A binascii.Error is raised if the input
+    is incorrectly padded.  Characters that are not in the standard alphabet
+    are discarded prior to the padding check.
+    """
+    return b64decode(s)
+
+
+_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
+_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
+
+def urlsafe_b64encode(s):
+    """Encode bytes using the URL- and filesystem-safe Base64 alphabet.
+
+    Argument s is a bytes-like object to encode.  The result is returned as a
+    bytes object.  The alphabet uses '-' instead of '+' and '_' instead of
+    '/'.
+    """
+    return b64encode(s).translate(_urlsafe_encode_translation)
+
+def urlsafe_b64decode(s):
+    """Decode bytes using the URL- and filesystem-safe Base64 alphabet.
+
+    Argument s is a bytes-like object or ASCII string to decode.  The result
+    is returned as a bytes object.  A binascii.Error is raised if the input
+    is incorrectly padded.  Characters that are not in the URL-safe base-64
+    alphabet, and are not a plus '+' or slash '/', are discarded prior to the
+    padding check.
+
+    The alphabet uses '-' instead of '+' and '_' instead of '/'.
+    """
+    s = _bytes_from_decode_data(s)
+    s = s.translate(_urlsafe_decode_translation)
+    return b64decode(s)
+
+
+
+# Base32 encoding/decoding must be done in Python
+_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
+_b32tab2 = None
+_b32rev = None
+
+def b32encode(s):
+    """Encode the bytes-like object s using Base32 and return a bytes object.
+    """
+    global _b32tab2
+    # Delay the initialization of the table to not waste memory
+    # if the function is never called
+    if _b32tab2 is None:
+        b32tab = [bytes((i,)) for i in _b32alphabet]
+        _b32tab2 = [a + b for a in b32tab for b in b32tab]
+        b32tab = None
+
+    if not isinstance(s, bytes_types):
+        s = memoryview(s).tobytes()
+    leftover = len(s) % 5
+    # Pad the last quantum with zero bits if necessary
+    if leftover:
+        s = s + b'\0' * (5 - leftover)  # Don't use += !
+    encoded = bytearray()
+    from_bytes = int.from_bytes
+    b32tab2 = _b32tab2
+    for i in range(0, len(s), 5):
+        c = from_bytes(s[i: i + 5], 'big')
+        encoded += (b32tab2[c >> 30] +           # bits 1 - 10
+                    b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
+                    b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
+                    b32tab2[c & 0x3ff]           # bits 31 - 40
+                   )
+    # Adjust for any leftover partial quanta
+    if leftover == 1:
+        encoded[-6:] = b'======'
+    elif leftover == 2:
+        encoded[-4:] = b'===='
+    elif leftover == 3:
+        encoded[-3:] = b'==='
+    elif leftover == 4:
+        encoded[-1:] = b'='
+    return bytes(encoded)
+
+def b32decode(s, casefold=False, map01=None):
+    """Decode the Base32 encoded bytes-like object or ASCII string s.
+
+    Optional casefold is a flag specifying whether a lowercase alphabet is
+    acceptable as input.  For security purposes, the default is False.
+
+    RFC 3548 allows for optional mapping of the digit 0 (zero) to the
+    letter O (oh), and for optional mapping of the digit 1 (one) to
+    either the letter I (eye) or letter L (el).  The optional argument
+    map01 when not None, specifies which letter the digit 1 should be
+    mapped to (when map01 is not None, the digit 0 is always mapped to
+    the letter O).  For security purposes the default is None, so that
+    0 and 1 are not allowed in the input.
+
+    The result is returned as a bytes object.  A binascii.Error is raised if
+    the input is incorrectly padded or if there are non-alphabet
+    characters present in the input.
+    """
+    global _b32rev
+    # Delay the initialization of the table to not waste memory
+    # if the function is never called
+    if _b32rev is None:
+        _b32rev = {v: k for k, v in enumerate(_b32alphabet)}
+    s = _bytes_from_decode_data(s)
+    if len(s) % 8:
+        raise binascii.Error('Incorrect padding')
+    # Handle section 2.4 zero and one mapping.  The flag map01 will be either
+    # False, or the character to map the digit 1 (one) to.  It should be
+    # either L (el) or I (eye).
+    if map01 is not None:
+        map01 = _bytes_from_decode_data(map01)
+        assert len(map01) == 1, repr(map01)
+        s = s.translate(bytes.maketrans(b'01', b'O' + map01))
+    if casefold:
+        s = s.upper()
+    # Strip off pad characters from the right.  We need to count the pad
+    # characters because this will tell us how many null bytes to remove from
+    # the end of the decoded string.
+    l = len(s)
+    s = s.rstrip(b'=')
+    padchars = l - len(s)
+    # Now decode the full quanta
+    decoded = bytearray()
+    b32rev = _b32rev
+    for i in range(0, len(s), 8):
+        quanta = s[i: i + 8]
+        acc = 0
+        try:
+            for c in quanta:
+                acc = (acc << 5) + b32rev[c]
+        except KeyError:
+            raise binascii.Error('Non-base32 digit found') from None
+        decoded += acc.to_bytes(5, 'big')
+    # Process the last, partial quanta
+    if l % 8 or padchars not in {0, 1, 3, 4, 6}:
+        raise binascii.Error('Incorrect padding')
+    if padchars and decoded:
+        acc <<= 5 * padchars
+        last = acc.to_bytes(5, 'big')
+        leftover = (43 - 5 * padchars) // 8  # 1: 4, 3: 3, 4: 2, 6: 1
+        decoded[-5:] = last[:leftover]
+    return bytes(decoded)
+
+
+# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
+# lowercase.  The RFC also recommends against accepting input case
+# insensitively.
+def b16encode(s):
+    """Encode the bytes-like object s using Base16 and return a bytes object.
+    """
+    return binascii.hexlify(s).upper()
+
+
+def b16decode(s, casefold=False):
+    """Decode the Base16 encoded bytes-like object or ASCII string s.
+
+    Optional casefold is a flag specifying whether a lowercase alphabet is
+    acceptable as input.  For security purposes, the default is False.
+
+    The result is returned as a bytes object.  A binascii.Error is raised if
+    s is incorrectly padded or if there are non-alphabet characters present
+    in the input.
+    """
+    s = _bytes_from_decode_data(s)
+    if casefold:
+        s = s.upper()
+    if re.search(b'[^0-9A-F]', s):
+        raise binascii.Error('Non-base16 digit found')
+    return binascii.unhexlify(s)
+
+#
+# Ascii85 encoding/decoding
+#
+
+_a85chars = None
+_a85chars2 = None
+_A85START = b"<~"
+_A85END = b"~>"
+
+def _85encode(b, chars, chars2, pad=False, foldnuls=False, foldspaces=False):
+    # Helper function for a85encode and b85encode
+    if not isinstance(b, bytes_types):
+        b = memoryview(b).tobytes()
+
+    padding = (-len(b)) % 4
+    if padding:
+        b = b + b'\0' * padding
+    words = struct.Struct('!%dI' % (len(b) // 4)).unpack(b)
+
+    chunks = [b'z' if foldnuls and not word else
+              b'y' if foldspaces and word == 0x20202020 else
+              (chars2[word // 614125] +
+               chars2[word // 85 % 7225] +
+               chars[word % 85])
+              for word in words]
+
+    if padding and not pad:
+        if chunks[-1] == b'z':
+            chunks[-1] = chars[0] * 5
+        chunks[-1] = chunks[-1][:-padding]
+
+    return b''.join(chunks)
+
+def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
+    """Encode bytes-like object b using Ascii85 and return a bytes object.
+
+    foldspaces is an optional flag that uses the special short sequence 'y'
+    instead of 4 consecutive spaces (ASCII 0x20) as supported by 'btoa'. This
+    feature is not supported by the "standard" Adobe encoding.
+
+    wrapcol controls whether the output should have newline (b'\\n') characters
+    added to it. If this is non-zero, each output line will be at most this
+    many characters long.
+
+    pad controls whether the input is padded to a multiple of 4 before
+    encoding. Note that the btoa implementation always pads.
+
+    adobe controls whether the encoded byte sequence is framed with <~ and ~>,
+    which is used by the Adobe implementation.
+    """
+    global _a85chars, _a85chars2
+    # Delay the initialization of tables to not waste memory
+    # if the function is never called
+    if _a85chars is None:
+        _a85chars = [bytes((i,)) for i in range(33, 118)]
+        _a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
+
+    result = _85encode(b, _a85chars, _a85chars2, pad, True, foldspaces)
+
+    if adobe:
+        result = _A85START + result
+    if wrapcol:
+        wrapcol = max(2 if adobe else 1, wrapcol)
+        chunks = [result[i: i + wrapcol]
+                  for i in range(0, len(result), wrapcol)]
+        if adobe:
+            if len(chunks[-1]) + 2 > wrapcol:
+                chunks.append(b'')
+        result = b'\n'.join(chunks)
+    if adobe:
+        result += _A85END
+
+    return result
+
+def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v'):
+    """Decode the Ascii85 encoded bytes-like object or ASCII string b.
+
+    foldspaces is a flag that specifies whether the 'y' short sequence should be
+    accepted as shorthand for 4 consecutive spaces (ASCII 0x20). This feature is
+    not supported by the "standard" Adobe encoding.
+
+    adobe controls whether the input sequence is in Adobe Ascii85 format (i.e.
+    is framed with <~ and ~>).
+
+    ignorechars should be a byte string containing characters to ignore from the
+    input. This should only contain whitespace characters, and by default
+    contains all whitespace characters in ASCII.
+
+    The result is returned as a bytes object.
+    """
+    b = _bytes_from_decode_data(b)
+    if adobe:
+        if not b.endswith(_A85END):
+            raise ValueError(
+                "Ascii85 encoded byte sequences must end "
+                "with {!r}".format(_A85END)
+                )
+        if b.startswith(_A85START):
+            b = b[2:-2]  # Strip off start/end markers
+        else:
+            b = b[:-2]
+    #
+    # We have to go through this stepwise, so as to ignore spaces and handle
+    # special short sequences
+    #
+    packI = struct.Struct('!I').pack
+    decoded = []
+    decoded_append = decoded.append
+    curr = []
+    curr_append = curr.append
+    curr_clear = curr.clear
+    for x in b + b'u' * 4:
+        if b'!'[0] <= x <= b'u'[0]:
+            curr_append(x)
+            if len(curr) == 5:
+                acc = 0
+                for x in curr:
+                    acc = 85 * acc + (x - 33)
+                try:
+                    decoded_append(packI(acc))
+                except struct.error:
+                    raise ValueError('Ascii85 overflow') from None
+                curr_clear()
+        elif x == b'z'[0]:
+            if curr:
+                raise ValueError('z inside Ascii85 5-tuple')
+            decoded_append(b'\0\0\0\0')
+        elif foldspaces and x == b'y'[0]:
+            if curr:
+                raise ValueError('y inside Ascii85 5-tuple')
+            decoded_append(b'\x20\x20\x20\x20')
+        elif x in ignorechars:
+            # Skip whitespace
+            continue
+        else:
+            raise ValueError('Non-Ascii85 digit found: %c' % x)
+
+    result = b''.join(decoded)
+    padding = 4 - len(curr)
+    if padding:
+        # Throw away the extra padding
+        result = result[:-padding]
+    return result
+
+# The following code is originally taken (with permission) from Mercurial
+
+_b85alphabet = (b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~")
+_b85chars = None
+_b85chars2 = None
+_b85dec = None
+
+def b85encode(b, pad=False):
+    """Encode bytes-like object b in base85 format and return a bytes object.
+
+    If pad is true, the input is padded with b'\\0' so its length is a multiple of
+    4 bytes before encoding.
+    """
+    global _b85chars, _b85chars2
+    # Delay the initialization of tables to not waste memory
+    # if the function is never called
+    if _b85chars is None:
+        _b85chars = [bytes((i,)) for i in _b85alphabet]
+        _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
+    return _85encode(b, _b85chars, _b85chars2, pad)
+
+def b85decode(b):
+    """Decode the base85-encoded bytes-like object or ASCII string b
+
+    The result is returned as a bytes object.
+    """
+    global _b85dec
+    # Delay the initialization of tables to not waste memory
+    # if the function is never called
+    if _b85dec is None:
+        _b85dec = [None] * 256
+        for i, c in enumerate(_b85alphabet):
+            _b85dec[c] = i
+
+    b = _bytes_from_decode_data(b)
+    padding = (-len(b)) % 5
+    b = b + b'~' * padding
+    out = []
+    packI = struct.Struct('!I').pack
+    for i in range(0, len(b), 5):
+        chunk = b[i:i + 5]
+        acc = 0
+        try:
+            for c in chunk:
+                acc = acc * 85 + _b85dec[c]
+        except TypeError:
+            for j, c in enumerate(chunk):
+                if _b85dec[c] is None:
+                    raise ValueError('bad base85 character at position %d'
+                                    % (i + j)) from None
+            raise
+        try:
+            out.append(packI(acc))
+        except struct.error:
+            raise ValueError('base85 overflow in hunk starting at byte %d'
+                             % i) from None
+
+    result = b''.join(out)
+    if padding:
+        result = result[:-padding]
+    return result
+
+# Legacy interface.  This code could be cleaned up since I don't believe
+# binascii has any line length limitations.  It just doesn't seem worth it
+# though.  The files should be opened in binary mode.
+
+MAXLINESIZE = 76 # Excluding the CRLF
+MAXBINSIZE = (MAXLINESIZE//4)*3
+
+def encode(input, output):
+    """Encode a file; input and output are binary files."""
+    while True:
+        s = input.read(MAXBINSIZE)
+        if not s:
+            break
+        while len(s) < MAXBINSIZE:
+            ns = input.read(MAXBINSIZE-len(s))
+            if not ns:
+                break
+            s += ns
+        line = binascii.b2a_base64(s)
+        output.write(line)
+
+
+def decode(input, output):
+    """Decode a file; input and output are binary files."""
+    while True:
+        line = input.readline()
+        if not line:
+            break
+        s = binascii.a2b_base64(line)
+        output.write(s)
+
+def _input_type_check(s):
+    try:
+        m = memoryview(s)
+    except TypeError as err:
+        msg = "expected bytes-like object, not %s" % s.__class__.__name__
+        raise TypeError(msg) from err
+    if m.format not in ('c', 'b', 'B'):
+        msg = ("expected single byte elements, not %r from %s" %
+                                          (m.format, s.__class__.__name__))
+        raise TypeError(msg)
+    if m.ndim != 1:
+        msg = ("expected 1-D data, not %d-D data from %s" %
+                                          (m.ndim, s.__class__.__name__))
+        raise TypeError(msg)
+
+
+def encodebytes(s):
+    """Encode a bytestring into a bytes object containing multiple lines
+    of base-64 data."""
+    _input_type_check(s)
+    pieces = []
+    for i in range(0, len(s), MAXBINSIZE):
+        chunk = s[i : i + MAXBINSIZE]
+        pieces.append(binascii.b2a_base64(chunk))
+    return b"".join(pieces)
+
+def encodestring(s):
+    """Legacy alias of encodebytes()."""
+    import warnings
+    warnings.warn("encodestring() is a deprecated alias since 3.1, "
+                  "use encodebytes()",
+                  DeprecationWarning, 2)
+    return encodebytes(s)
+
+
+def decodebytes(s):
+    """Decode a bytestring of base-64 data into a bytes object."""
+    _input_type_check(s)
+    return binascii.a2b_base64(s)
+
+def decodestring(s):
+    """Legacy alias of decodebytes()."""
+    import warnings
+    warnings.warn("decodestring() is a deprecated alias since Python 3.1, "
+                  "use decodebytes()",
+                  DeprecationWarning, 2)
+    return decodebytes(s)
+
+
+# Usable as a script...
+def main():
+    """Small main program"""
+    import sys, getopt
+    try:
+        opts, args = getopt.getopt(sys.argv[1:], 'deut')
+    except getopt.error as msg:
+        sys.stdout = sys.stderr
+        print(msg)
+        print("""usage: %s [-d|-e|-u|-t] [file|-]
+        -d, -u: decode
+        -e: encode (default)
+        -t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0])
+        sys.exit(2)
+    func = encode
+    for o, a in opts:
+        if o == '-e': func = encode
+        if o == '-d': func = decode
+        if o == '-u': func = decode
+        if o == '-t': test(); return
+    if args and args[0] != '-':
+        with open(args[0], 'rb') as f:
+            func(f, sys.stdout.buffer)
+    else:
+        func(sys.stdin.buffer, sys.stdout.buffer)
+
+
+def test():
+    s0 = b"Aladdin:open sesame"
+    print(repr(s0))
+    s1 = encodebytes(s0)
+    print(repr(s1))
+    s2 = decodebytes(s1)
+    print(repr(s2))
+    assert s0 == s2
+
+
+if __name__ == '__main__':
+    main()
diff --git a/Lib/bisect.py b/Lib/bisect.py
new file mode 100644
index 000000000..4a4d05255
--- /dev/null
+++ b/Lib/bisect.py
@@ -0,0 +1,92 @@
+"""Bisection algorithms."""
+
+def insort_right(a, x, lo=0, hi=None):
+    """Insert item x in list a, and keep it sorted assuming a is sorted.
+
+    If x is already in a, insert it to the right of the rightmost x.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if x < a[mid]: hi = mid
+        else: lo = mid+1
+    a.insert(lo, x)
+
+insort = insort_right   # backward compatibility
+
+def bisect_right(a, x, lo=0, hi=None):
+    """Return the index where to insert item x in list a, assuming a is sorted.
+
+    The return value i is such that all e in a[:i] have e <= x, and all e in
+    a[i:] have e > x.  So if x already appears in the list, a.insert(x) will
+    insert just after the rightmost x already there.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if x < a[mid]: hi = mid
+        else: lo = mid+1
+    return lo
+
+bisect = bisect_right   # backward compatibility
+
+def insort_left(a, x, lo=0, hi=None):
+    """Insert item x in list a, and keep it sorted assuming a is sorted.
+
+    If x is already in a, insert it to the left of the leftmost x.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if a[mid] < x: lo = mid+1
+        else: hi = mid
+    a.insert(lo, x)
+
+
+def bisect_left(a, x, lo=0, hi=None):
+    """Return the index where to insert item x in list a, assuming a is sorted.
+
+    The return value i is such that all e in a[:i] have e < x, and all e in
+    a[i:] have e >= x.  So if x already appears in the list, a.insert(x) will
+    insert just before the leftmost x already there.
+
+    Optional args lo (default 0) and hi (default len(a)) bound the
+    slice of a to be searched.
+    """
+
+    if lo < 0:
+        raise ValueError('lo must be non-negative')
+    if hi is None:
+        hi = len(a)
+    while lo < hi:
+        mid = (lo+hi)//2
+        if a[mid] < x: lo = mid+1
+        else: hi = mid
+    return lo
+
+# Overwrite above definitions with a fast C implementation
+try:
+    from _bisect import *
+except ImportError:
+    pass
diff --git a/Lib/chunk.py b/Lib/chunk.py
new file mode 100644
index 000000000..d94dd3980
--- /dev/null
+++ b/Lib/chunk.py
@@ -0,0 +1,169 @@
+"""Simple class to read IFF chunks.
+
+An IFF chunk (used in formats such as AIFF, TIFF, RMFF (RealMedia File
+Format)) has the following structure:
+
++----------------+
+| ID (4 bytes)   |
++----------------+
+| size (4 bytes) |
++----------------+
+| data           |
+| ...            |
++----------------+
+
+The ID is a 4-byte string which identifies the type of chunk.
+
+The size field (a 32-bit value, encoded using big-endian byte order)
+gives the size of the whole chunk, including the 8-byte header.
+
+Usually an IFF-type file consists of one or more chunks.  The proposed
+usage of the Chunk class defined here is to instantiate an instance at
+the start of each chunk and read from the instance until it reaches
+the end, after which a new instance can be instantiated.  At the end
+of the file, creating a new instance will fail with an EOFError
+exception.
+
+Usage:
+while True:
+    try:
+        chunk = Chunk(file)
+    except EOFError:
+        break
+    chunktype = chunk.getname()
+    while True:
+        data = chunk.read(nbytes)
+        if not data:
+            pass
+        # do something with data
+
+The interface is file-like.  The implemented methods are:
+read, close, seek, tell, isatty.
+Extra methods are: skip() (called by close, skips to the end of the chunk),
+getname() (returns the name (ID) of the chunk)
+
+The __init__ method has one required argument, a file-like object
+(including a chunk instance), and one optional argument, a flag which
+specifies whether or not chunks are aligned on 2-byte boundaries.  The
+default is 1, i.e. aligned.
+"""
+
+class Chunk:
+    def __init__(self, file, align=True, bigendian=True, inclheader=False):
+        import struct
+        self.closed = False
+        self.align = align      # whether to align to word (2-byte) boundaries
+        if bigendian:
+            strflag = '>'
+        else:
+            strflag = '<'
+        self.file = file
+        self.chunkname = file.read(4)
+        if len(self.chunkname) < 4:
+            raise EOFError
+        try:
+            self.chunksize = struct.unpack_from(strflag+'L', file.read(4))[0]
+        except struct.error:
+            raise EOFError
+        if inclheader:
+            self.chunksize = self.chunksize - 8 # subtract header
+        self.size_read = 0
+        try:
+            self.offset = self.file.tell()
+        except (AttributeError, OSError):
+            self.seekable = False
+        else:
+            self.seekable = True
+
+    def getname(self):
+        """Return the name (ID) of the current chunk."""
+        return self.chunkname
+
+    def getsize(self):
+        """Return the size of the current chunk."""
+        return self.chunksize
+
+    def close(self):
+        if not self.closed:
+            try:
+                self.skip()
+            finally:
+                self.closed = True
+
+    def isatty(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        return False
+
+    def seek(self, pos, whence=0):
+        """Seek to specified position into the chunk.
+        Default position is 0 (start of chunk).
+        If the file is not seekable, this will result in an error.
+        """
+
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        if not self.seekable:
+            raise OSError("cannot seek")
+        if whence == 1:
+            pos = pos + self.size_read
+        elif whence == 2:
+            pos = pos + self.chunksize
+        if pos < 0 or pos > self.chunksize:
+            raise RuntimeError
+        self.file.seek(self.offset + pos, 0)
+        self.size_read = pos
+
+    def tell(self):
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        return self.size_read
+
+    def read(self, size=-1):
+        """Read at most size bytes from the chunk.
+        If size is omitted or negative, read until the end
+        of the chunk.
+        """
+
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        if self.size_read >= self.chunksize:
+            return b''
+        if size < 0:
+            size = self.chunksize - self.size_read
+        if size > self.chunksize - self.size_read:
+            size = self.chunksize - self.size_read
+        data = self.file.read(size)
+        self.size_read = self.size_read + len(data)
+        if self.size_read == self.chunksize and \
+           self.align and \
+           (self.chunksize & 1):
+            dummy = self.file.read(1)
+            self.size_read = self.size_read + len(dummy)
+        return data
+
+    def skip(self):
+        """Skip the rest of the chunk.
+        If you are not interested in the contents of the chunk,
+        this method should be called so that the file points to
+        the start of the next chunk.
+        """
+
+        if self.closed:
+            raise ValueError("I/O operation on closed file")
+        if self.seekable:
+            try:
+                n = self.chunksize - self.size_read
+                # maybe fix alignment
+                if self.align and (self.chunksize & 1):
+                    n = n + 1
+                self.file.seek(n, 1)
+                self.size_read = self.size_read + n
+                return
+            except OSError:
+                pass
+        while self.size_read < self.chunksize:
+            n = min(8192, self.chunksize - self.size_read)
+            dummy = self.read(n)
+            if not dummy:
+                raise EOFError
diff --git a/Lib/codeop.py b/Lib/codeop.py
new file mode 100644
index 000000000..fb759da42
--- /dev/null
+++ b/Lib/codeop.py
@@ -0,0 +1,168 @@
+r"""Utilities to compile possibly incomplete Python source code.
+
+This module provides two interfaces, broadly similar to the builtin
+function compile(), which take program text, a filename and a 'mode'
+and:
+
+- Return code object if the command is complete and valid
+- Return None if the command is incomplete
+- Raise SyntaxError, ValueError or OverflowError if the command is a
+  syntax error (OverflowError and ValueError can be produced by
+  malformed literals).
+
+Approach:
+
+First, check if the source consists entirely of blank lines and
+comments; if so, replace it with 'pass', because the built-in
+parser doesn't always do the right thing for these.
+
+Compile three times: as is, with \n, and with \n\n appended.  If it
+compiles as is, it's complete.  If it compiles with one \n appended,
+we expect more.  If it doesn't compile either way, we compare the
+error we get when compiling with \n or \n\n appended.  If the errors
+are the same, the code is broken.  But if the errors are different, we
+expect more.  Not intuitive; not even guaranteed to hold in future
+releases; but this matches the compiler's behavior from Python 1.4
+through 2.2, at least.
+
+Caveat:
+
+It is possible (but not likely) that the parser stops parsing with a
+successful outcome before reaching the end of the source; in this
+case, trailing symbols may be ignored instead of causing an error.
+For example, a backslash followed by two newlines may be followed by
+arbitrary garbage.  This will be fixed once the API for the parser is
+better.
+
+The two interfaces are:
+
+compile_command(source, filename, symbol):
+
+    Compiles a single command in the manner described above.
+
+CommandCompiler():
+
+    Instances of this class have __call__ methods identical in
+    signature to compile_command; the difference is that if the
+    instance compiles program text containing a __future__ statement,
+    the instance 'remembers' and compiles all subsequent program texts
+    with the statement in force.
+
+The module also provides another class:
+
+Compile():
+
+    Instances of this class act like the built-in function compile,
+    but with 'memory' in the sense described above.
+"""
+
+import __future__
+
+_features = [getattr(__future__, fname)
+             for fname in __future__.all_feature_names]
+
+__all__ = ["compile_command", "Compile", "CommandCompiler"]
+
+PyCF_DONT_IMPLY_DEDENT = 0x200          # Matches pythonrun.h
+
+def _maybe_compile(compiler, source, filename, symbol):
+    # Check for source consisting of only blank lines and comments
+    for line in source.split("\n"):
+        line = line.strip()
+        if line and line[0] != '#':
+            break               # Leave it alone
+    else:
+        if symbol != "eval":
+            source = "pass"     # Replace it with a 'pass' statement
+
+    err = err1 = err2 = None
+    code = code1 = code2 = None
+
+    try:
+        code = compiler(source, filename, symbol)
+    except SyntaxError as err:
+        pass
+
+    try:
+        code1 = compiler(source + "\n", filename, symbol)
+    except SyntaxError as e:
+        err1 = e
+
+    try:
+        code2 = compiler(source + "\n\n", filename, symbol)
+    except SyntaxError as e:
+        err2 = e
+
+    if code:
+        return code
+    if not code1 and repr(err1) == repr(err2):
+        raise err1
+
+def _compile(source, filename, symbol):
+    return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT)
+
+def compile_command(source, filename="<input>", symbol="single"):
+    r"""Compile a command and determine whether it is incomplete.
+
+    Arguments:
+
+    source -- the source string; may contain \n characters
+    filename -- optional filename from which source was read; default
+                "<input>"
+    symbol -- optional grammar start symbol; "single" (default) or "eval"
+
+    Return value / exceptions raised:
+
+    - Return a code object if the command is complete and valid
+    - Return None if the command is incomplete
+    - Raise SyntaxError, ValueError or OverflowError if the command is a
+      syntax error (OverflowError and ValueError can be produced by
+      malformed literals).
+    """
+    return _maybe_compile(_compile, source, filename, symbol)
+
+class Compile:
+    """Instances of this class behave much like the built-in compile
+    function, but if one is used to compile text containing a future
+    statement, it "remembers" and compiles all subsequent program texts
+    with the statement in force."""
+    def __init__(self):
+        self.flags = PyCF_DONT_IMPLY_DEDENT
+
+    def __call__(self, source, filename, symbol):
+        codeob = compile(source, filename, symbol, self.flags, 1)
+        for feature in _features:
+            if codeob.co_flags & feature.compiler_flag:
+                self.flags |= feature.compiler_flag
+        return codeob
+
+class CommandCompiler:
+    """Instances of this class have __call__ methods identical in
+    signature to compile_command; the difference is that if the
+    instance compiles program text containing a __future__ statement,
+    the instance 'remembers' and compiles all subsequent program texts
+    with the statement in force."""
+
+    def __init__(self,):
+        self.compiler = Compile()
+
+    def __call__(self, source, filename="<input>", symbol="single"):
+        r"""Compile a command and determine whether it is incomplete.
+
+        Arguments:
+
+        source -- the source string; may contain \n characters
+        filename -- optional filename from which source was read;
+                    default "<input>"
+        symbol -- optional grammar start symbol; "single" (default) or
+                  "eval"
+
+        Return value / exceptions raised:
+
+        - Return a code object if the command is complete and valid
+        - Return None if the command is incomplete
+        - Raise SyntaxError, ValueError or OverflowError if the command is a
+          syntax error (OverflowError and ValueError can be produced by
+          malformed literals).
+        """
+        return _maybe_compile(self.compiler, source, filename, symbol)
diff --git a/Lib/copyreg.py b/Lib/copyreg.py
new file mode 100644
index 000000000..cef9984b1
--- /dev/null
+++ b/Lib/copyreg.py
@@ -0,0 +1,206 @@
+"""Helper to provide extensibility for pickle.
+
+This is only useful to add pickle support for extension types defined in
+C, not for instances of user-defined classes.
+"""
+
+__all__ = ["pickle", "constructor",
+           "add_extension", "remove_extension", "clear_extension_cache"]
+
+dispatch_table = {}
+
+def pickle(ob_type, pickle_function, constructor_ob=None):
+    if not callable(pickle_function):
+        raise TypeError("reduction functions must be callable")
+    dispatch_table[ob_type] = pickle_function
+
+    # The constructor_ob function is a vestige of safe for unpickling.
+    # There is no reason for the caller to pass it anymore.
+    if constructor_ob is not None:
+        constructor(constructor_ob)
+
+def constructor(object):
+    if not callable(object):
+        raise TypeError("constructors must be callable")
+
+# Example: provide pickling support for complex numbers.
+
+try:
+    complex
+except NameError:
+    pass
+else:
+
+    def pickle_complex(c):
+        return complex, (c.real, c.imag)
+
+    pickle(complex, pickle_complex, complex)
+
+# Support for pickling new-style objects
+
+def _reconstructor(cls, base, state):
+    if base is object:
+        obj = object.__new__(cls)
+    else:
+        obj = base.__new__(cls, state)
+        if base.__init__ != object.__init__:
+            base.__init__(obj, state)
+    return obj
+
+_HEAPTYPE = 1<<9
+
+# Python code for object.__reduce_ex__ for protocols 0 and 1
+
+def _reduce_ex(self, proto):
+    assert proto < 2
+    for base in self.__class__.__mro__:
+        if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
+            break
+    else:
+        base = object # not really reachable
+    if base is object:
+        state = None
+    else:
+        if base is self.__class__:
+            raise TypeError("can't pickle %s objects" % base.__name__)
+        state = base(self)
+    args = (self.__class__, base, state)
+    try:
+        getstate = self.__getstate__
+    except AttributeError:
+        if getattr(self, "__slots__", None):
+            raise TypeError("a class that defines __slots__ without "
+                            "defining __getstate__ cannot be pickled")
+        try:
+            dict = self.__dict__
+        except AttributeError:
+            dict = None
+    else:
+        dict = getstate()
+    if dict:
+        return _reconstructor, args, dict
+    else:
+        return _reconstructor, args
+
+# Helper for __reduce_ex__ protocol 2
+
+def __newobj__(cls, *args):
+    return cls.__new__(cls, *args)
+
+def __newobj_ex__(cls, args, kwargs):
+    """Used by pickle protocol 4, instead of __newobj__ to allow classes with
+    keyword-only arguments to be pickled correctly.
+    """
+    return cls.__new__(cls, *args, **kwargs)
+
+def _slotnames(cls):
+    """Return a list of slot names for a given class.
+
+    This needs to find slots defined by the class and its bases, so we
+    can't simply return the __slots__ attribute.  We must walk down
+    the Method Resolution Order and concatenate the __slots__ of each
+    class found there.  (This assumes classes don't modify their
+    __slots__ attribute to misrepresent their slots after the class is
+    defined.)
+    """
+
+    # Get the value from a cache in the class if possible
+    names = cls.__dict__.get("__slotnames__")
+    if names is not None:
+        return names
+
+    # Not cached -- calculate the value
+    names = []
+    if not hasattr(cls, "__slots__"):
+        # This class has no slots
+        pass
+    else:
+        # Slots found -- gather slot names from all base classes
+        for c in cls.__mro__:
+            if "__slots__" in c.__dict__:
+                slots = c.__dict__['__slots__']
+                # if class has a single slot, it can be given as a string
+                if isinstance(slots, str):
+                    slots = (slots,)
+                for name in slots:
+                    # special descriptors
+                    if name in ("__dict__", "__weakref__"):
+                        continue
+                    # mangled names
+                    elif name.startswith('__') and not name.endswith('__'):
+                        stripped = c.__name__.lstrip('_')
+                        if stripped:
+                            names.append('_%s%s' % (stripped, name))
+                        else:
+                            names.append(name)
+                    else:
+                        names.append(name)
+
+    # Cache the outcome in the class if at all possible
+    try:
+        cls.__slotnames__ = names
+    except:
+        pass # But don't die if we can't
+
+    return names
+
+# A registry of extension codes.  This is an ad-hoc compression
+# mechanism.  Whenever a global reference to <module>, <name> is about
+# to be pickled, the (<module>, <name>) tuple is looked up here to see
+# if it is a registered extension code for it.  Extension codes are
+# universal, so that the meaning of a pickle does not depend on
+# context.  (There are also some codes reserved for local use that
+# don't have this restriction.)  Codes are positive ints; 0 is
+# reserved.
+
+_extension_registry = {}                # key -> code
+_inverted_registry = {}                 # code -> key
+_extension_cache = {}                   # code -> object
+# Don't ever rebind those names:  pickling grabs a reference to them when
+# it's initialized, and won't see a rebinding.
+
+def add_extension(module, name, code):
+    """Register an extension code."""
+    code = int(code)
+    if not 1 <= code <= 0x7fffffff:
+        raise ValueError("code out of range")
+    key = (module, name)
+    if (_extension_registry.get(key) == code and
+        _inverted_registry.get(code) == key):
+        return # Redundant registrations are benign
+    if key in _extension_registry:
+        raise ValueError("key %s is already registered with code %s" %
+                         (key, _extension_registry[key]))
+    if code in _inverted_registry:
+        raise ValueError("code %s is already in use for key %s" %
+                         (code, _inverted_registry[code]))
+    _extension_registry[key] = code
+    _inverted_registry[code] = key
+
+def remove_extension(module, name, code):
+    """Unregister an extension code.  For testing only."""
+    key = (module, name)
+    if (_extension_registry.get(key) != code or
+        _inverted_registry.get(code) != key):
+        raise ValueError("key %s is not registered with code %s" %
+                         (key, code))
+    del _extension_registry[key]
+    del _inverted_registry[code]
+    if code in _extension_cache:
+        del _extension_cache[code]
+
+def clear_extension_cache():
+    _extension_cache.clear()
+
+# Standard extension code assignments
+
+# Reserved ranges
+
+# First  Last Count  Purpose
+#     1   127   127  Reserved for Python standard library
+#   128   191    64  Reserved for Zope
+#   192   239    48  Reserved for 3rd parties
+#   240   255    16  Reserved for private use (will never be assigned)
+#   256   Inf   Inf  Reserved for future assignment
+
+# Extension codes are assigned by the Python Software Foundation.
diff --git a/Lib/formatter.py b/Lib/formatter.py
new file mode 100644
index 000000000..e2394de8c
--- /dev/null
+++ b/Lib/formatter.py
@@ -0,0 +1,452 @@
+"""Generic output formatting.
+
+Formatter objects transform an abstract flow of formatting events into
+specific output events on writer objects. Formatters manage several stack
+structures to allow various properties of a writer object to be changed and
+restored; writers need not be able to handle relative changes nor any sort
+of ``change back'' operation. Specific writer properties which may be
+controlled via formatter objects are horizontal alignment, font, and left
+margin indentations. A mechanism is provided which supports providing
+arbitrary, non-exclusive style settings to a writer as well. Additional
+interfaces facilitate formatting events which are not reversible, such as
+paragraph separation.
+
+Writer objects encapsulate device interfaces. Abstract devices, such as
+file formats, are supported as well as physical devices. The provided
+implementations all work with abstract devices. The interface makes
+available mechanisms for setting the properties which formatter objects
+manage and inserting data into the output.
+"""
+
+import sys
+import warnings
+warnings.warn('the formatter module is deprecated', DeprecationWarning,
+              stacklevel=2)
+
+
+AS_IS = None
+
+
+class NullFormatter:
+    """A formatter which does nothing.
+
+    If the writer parameter is omitted, a NullWriter instance is created.
+    No methods of the writer are called by NullFormatter instances.
+
+    Implementations should inherit from this class if implementing a writer
+    interface but don't need to inherit any implementation.
+
+    """
+
+    def __init__(self, writer=None):
+        if writer is None:
+            writer = NullWriter()
+        self.writer = writer
+    def end_paragraph(self, blankline): pass
+    def add_line_break(self): pass
+    def add_hor_rule(self, *args, **kw): pass
+    def add_label_data(self, format, counter, blankline=None): pass
+    def add_flowing_data(self, data): pass
+    def add_literal_data(self, data): pass
+    def flush_softspace(self): pass
+    def push_alignment(self, align): pass
+    def pop_alignment(self): pass
+    def push_font(self, x): pass
+    def pop_font(self): pass
+    def push_margin(self, margin): pass
+    def pop_margin(self): pass
+    def set_spacing(self, spacing): pass
+    def push_style(self, *styles): pass
+    def pop_style(self, n=1): pass
+    def assert_line_data(self, flag=1): pass
+
+
+class AbstractFormatter:
+    """The standard formatter.
+
+    This implementation has demonstrated wide applicability to many writers,
+    and may be used directly in most circumstances.  It has been used to
+    implement a full-featured World Wide Web browser.
+
+    """
+
+    #  Space handling policy:  blank spaces at the boundary between elements
+    #  are handled by the outermost context.  "Literal" data is not checked
+    #  to determine context, so spaces in literal data are handled directly
+    #  in all circumstances.
+
+    def __init__(self, writer):
+        self.writer = writer            # Output device
+        self.align = None               # Current alignment
+        self.align_stack = []           # Alignment stack
+        self.font_stack = []            # Font state
+        self.margin_stack = []          # Margin state
+        self.spacing = None             # Vertical spacing state
+        self.style_stack = []           # Other state, e.g. color
+        self.nospace = 1                # Should leading space be suppressed
+        self.softspace = 0              # Should a space be inserted
+        self.para_end = 1               # Just ended a paragraph
+        self.parskip = 0                # Skipped space between paragraphs?
+        self.hard_break = 1             # Have a hard break
+        self.have_label = 0
+
+    def end_paragraph(self, blankline):
+        if not self.hard_break:
+            self.writer.send_line_break()
+            self.have_label = 0
+        if self.parskip < blankline and not self.have_label:
+            self.writer.send_paragraph(blankline - self.parskip)
+            self.parskip = blankline
+            self.have_label = 0
+        self.hard_break = self.nospace = self.para_end = 1
+        self.softspace = 0
+
+    def add_line_break(self):
+        if not (self.hard_break or self.para_end):
+            self.writer.send_line_break()
+            self.have_label = self.parskip = 0
+        self.hard_break = self.nospace = 1
+        self.softspace = 0
+
+    def add_hor_rule(self, *args, **kw):
+        if not self.hard_break:
+            self.writer.send_line_break()
+        self.writer.send_hor_rule(*args, **kw)
+        self.hard_break = self.nospace = 1
+        self.have_label = self.para_end = self.softspace = self.parskip = 0
+
+    def add_label_data(self, format, counter, blankline = None):
+        if self.have_label or not self.hard_break:
+            self.writer.send_line_break()
+        if not self.para_end:
+            self.writer.send_paragraph((blankline and 1) or 0)
+        if isinstance(format, str):
+            self.writer.send_label_data(self.format_counter(format, counter))
+        else:
+            self.writer.send_label_data(format)
+        self.nospace = self.have_label = self.hard_break = self.para_end = 1
+        self.softspace = self.parskip = 0
+
+    def format_counter(self, format, counter):
+        label = ''
+        for c in format:
+            if c == '1':
+                label = label + ('%d' % counter)
+            elif c in 'aA':
+                if counter > 0:
+                    label = label + self.format_letter(c, counter)
+            elif c in 'iI':
+                if counter > 0:
+                    label = label + self.format_roman(c, counter)
+            else:
+                label = label + c
+        return label
+
+    def format_letter(self, case, counter):
+        label = ''
+        while counter > 0:
+            counter, x = divmod(counter-1, 26)
+            # This makes a strong assumption that lowercase letters
+            # and uppercase letters form two contiguous blocks, with
+            # letters in order!
+            s = chr(ord(case) + x)
+            label = s + label
+        return label
+
+    def format_roman(self, case, counter):
+        ones = ['i', 'x', 'c', 'm']
+        fives = ['v', 'l', 'd']
+        label, index = '', 0
+        # This will die of IndexError when counter is too big
+        while counter > 0:
+            counter, x = divmod(counter, 10)
+            if x == 9:
+                label = ones[index] + ones[index+1] + label
+            elif x == 4:
+                label = ones[index] + fives[index] + label
+            else:
+                if x >= 5:
+                    s = fives[index]
+                    x = x-5
+                else:
+                    s = ''
+                s = s + ones[index]*x
+                label = s + label
+            index = index + 1
+        if case == 'I':
+            return label.upper()
+        return label
+
+    def add_flowing_data(self, data):
+        if not data: return
+        prespace = data[:1].isspace()
+        postspace = data[-1:].isspace()
+        data = " ".join(data.split())
+        if self.nospace and not data:
+            return
+        elif prespace or self.softspace:
+            if not data:
+                if not self.nospace:
+                    self.softspace = 1
+                    self.parskip = 0
+                return
+            if not self.nospace:
+                data = ' ' + data
+        self.hard_break = self.nospace = self.para_end = \
+                          self.parskip = self.have_label = 0
+        self.softspace = postspace
+        self.writer.send_flowing_data(data)
+
+    def add_literal_data(self, data):
+        if not data: return
+        if self.softspace:
+            self.writer.send_flowing_data(" ")
+        self.hard_break = data[-1:] == '\n'
+        self.nospace = self.para_end = self.softspace = \
+                       self.parskip = self.have_label = 0
+        self.writer.send_literal_data(data)
+
+    def flush_softspace(self):
+        if self.softspace:
+            self.hard_break = self.para_end = self.parskip = \
+                              self.have_label = self.softspace = 0
+            self.nospace = 1
+            self.writer.send_flowing_data(' ')
+
+    def push_alignment(self, align):
+        if align and align != self.align:
+            self.writer.new_alignment(align)
+            self.align = align
+            self.align_stack.append(align)
+        else:
+            self.align_stack.append(self.align)
+
+    def pop_alignment(self):
+        if self.align_stack:
+            del self.align_stack[-1]
+        if self.align_stack:
+            self.align = align = self.align_stack[-1]
+            self.writer.new_alignment(align)
+        else:
+            self.align = None
+            self.writer.new_alignment(None)
+
+    def push_font(self, font):
+        size, i, b, tt = font
+        if self.softspace:
+            self.hard_break = self.para_end = self.softspace = 0
+            self.nospace = 1
+            self.writer.send_flowing_data(' ')
+        if self.font_stack:
+            csize, ci, cb, ctt = self.font_stack[-1]
+            if size is AS_IS: size = csize
+            if i is AS_IS: i = ci
+            if b is AS_IS: b = cb
+            if tt is AS_IS: tt = ctt
+        font = (size, i, b, tt)
+        self.font_stack.append(font)
+        self.writer.new_font(font)
+
+    def pop_font(self):
+        if self.font_stack:
+            del self.font_stack[-1]
+        if self.font_stack:
+            font = self.font_stack[-1]
+        else:
+            font = None
+        self.writer.new_font(font)
+
+    def push_margin(self, margin):
+        self.margin_stack.append(margin)
+        fstack = [m for m in self.margin_stack if m]
+        if not margin and fstack:
+            margin = fstack[-1]
+        self.writer.new_margin(margin, len(fstack))
+
+    def pop_margin(self):
+        if self.margin_stack:
+            del self.margin_stack[-1]
+        fstack = [m for m in self.margin_stack if m]
+        if fstack:
+            margin = fstack[-1]
+        else:
+            margin = None
+        self.writer.new_margin(margin, len(fstack))
+
+    def set_spacing(self, spacing):
+        self.spacing = spacing
+        self.writer.new_spacing(spacing)
+
+    def push_style(self, *styles):
+        if self.softspace:
+            self.hard_break = self.para_end = self.softspace = 0
+            self.nospace = 1
+            self.writer.send_flowing_data(' ')
+        for style in styles:
+            self.style_stack.append(style)
+        self.writer.new_styles(tuple(self.style_stack))
+
+    def pop_style(self, n=1):
+        del self.style_stack[-n:]
+        self.writer.new_styles(tuple(self.style_stack))
+
+    def assert_line_data(self, flag=1):
+        self.nospace = self.hard_break = not flag
+        self.para_end = self.parskip = self.have_label = 0
+
+
+class NullWriter:
+    """Minimal writer interface to use in testing & inheritance.
+
+    A writer which only provides the interface definition; no actions are
+    taken on any methods.  This should be the base class for all writers
+    which do not need to inherit any implementation methods.
+
+    """
+    def __init__(self): pass
+    def flush(self): pass
+    def new_alignment(self, align): pass
+    def new_font(self, font): pass
+    def new_margin(self, margin, level): pass
+    def new_spacing(self, spacing): pass
+    def new_styles(self, styles): pass
+    def send_paragraph(self, blankline): pass
+    def send_line_break(self): pass
+    def send_hor_rule(self, *args, **kw): pass
+    def send_label_data(self, data): pass
+    def send_flowing_data(self, data): pass
+    def send_literal_data(self, data): pass
+
+
+class AbstractWriter(NullWriter):
+    """A writer which can be used in debugging formatters, but not much else.
+
+    Each method simply announces itself by printing its name and
+    arguments on standard output.
+
+    """
+
+    def new_alignment(self, align):
+        print("new_alignment(%r)" % (align,))
+
+    def new_font(self, font):
+        print("new_font(%r)" % (font,))
+
+    def new_margin(self, margin, level):
+        print("new_margin(%r, %d)" % (margin, level))
+
+    def new_spacing(self, spacing):
+        print("new_spacing(%r)" % (spacing,))
+
+    def new_styles(self, styles):
+        print("new_styles(%r)" % (styles,))
+
+    def send_paragraph(self, blankline):
+        print("send_paragraph(%r)" % (blankline,))
+
+    def send_line_break(self):
+        print("send_line_break()")
+
+    def send_hor_rule(self, *args, **kw):
+        print("send_hor_rule()")
+
+    def send_label_data(self, data):
+        print("send_label_data(%r)" % (data,))
+
+    def send_flowing_data(self, data):
+        print("send_flowing_data(%r)" % (data,))
+
+    def send_literal_data(self, data):
+        print("send_literal_data(%r)" % (data,))
+
+
+class DumbWriter(NullWriter):
+    """Simple writer class which writes output on the file object passed in
+    as the file parameter or, if file is omitted, on standard output.  The
+    output is simply word-wrapped to the number of columns specified by
+    the maxcol parameter.  This class is suitable for reflowing a sequence
+    of paragraphs.
+
+    """
+
+    def __init__(self, file=None, maxcol=72):
+        self.file = file or sys.stdout
+        self.maxcol = maxcol
+        NullWriter.__init__(self)
+        self.reset()
+
+    def reset(self):
+        self.col = 0
+        self.atbreak = 0
+
+    def send_paragraph(self, blankline):
+        self.file.write('\n'*blankline)
+        self.col = 0
+        self.atbreak = 0
+
+    def send_line_break(self):
+        self.file.write('\n')
+        self.col = 0
+        self.atbreak = 0
+
+    def send_hor_rule(self, *args, **kw):
+        self.file.write('\n')
+        self.file.write('-'*self.maxcol)
+        self.file.write('\n')
+        self.col = 0
+        self.atbreak = 0
+
+    def send_literal_data(self, data):
+        self.file.write(data)
+        i = data.rfind('\n')
+        if i >= 0:
+            self.col = 0
+            data = data[i+1:]
+        data = data.expandtabs()
+        self.col = self.col + len(data)
+        self.atbreak = 0
+
+    def send_flowing_data(self, data):
+        if not data: return
+        atbreak = self.atbreak or data[0].isspace()
+        col = self.col
+        maxcol = self.maxcol
+        write = self.file.write
+        for word in data.split():
+            if atbreak:
+                if col + len(word) >= maxcol:
+                    write('\n')
+                    col = 0
+                else:
+                    write(' ')
+                    col = col + 1
+            write(word)
+            col = col + len(word)
+            atbreak = 1
+        self.col = col
+        self.atbreak = data[-1].isspace()
+
+
+def test(file = None):
+    w = DumbWriter()
+    f = AbstractFormatter(w)
+    if file is not None:
+        fp = open(file)
+    elif sys.argv[1:]:
+        fp = open(sys.argv[1])
+    else:
+        fp = sys.stdin
+    try:
+        for line in fp:
+            if line == '\n':
+                f.end_paragraph(1)
+            else:
+                f.add_flowing_data(line)
+    finally:
+        if fp is not sys.stdin:
+            fp.close()
+    f.end_paragraph(0)
+
+
+if __name__ == '__main__':
+    test()
diff --git a/Lib/nturl2path.py b/Lib/nturl2path.py
new file mode 100644
index 000000000..36dc76588
--- /dev/null
+++ b/Lib/nturl2path.py
@@ -0,0 +1,68 @@
+"""Convert a NT pathname to a file URL and vice versa."""
+
+def url2pathname(url):
+    """OS-specific conversion from a relative URL of the 'file' scheme
+    to a file system path; not recommended for general use."""
+    # e.g.
+    #   ///C|/foo/bar/spam.foo
+    # and
+    #   ///C:/foo/bar/spam.foo
+    # become
+    #   C:\foo\bar\spam.foo
+    import string, urllib.parse
+    # Windows itself uses ":" even in URLs.
+    url = url.replace(':', '|')
+    if not '|' in url:
+        # No drive specifier, just convert slashes
+        if url[:4] == '////':
+            # path is something like ////host/path/on/remote/host
+            # convert this to \\host\path\on\remote\host
+            # (notice halving of slashes at the start of the path)
+            url = url[2:]
+        components = url.split('/')
+        # make sure not to convert quoted slashes :-)
+        return urllib.parse.unquote('\\'.join(components))
+    comp = url.split('|')
+    if len(comp) != 2 or comp[0][-1] not in string.ascii_letters:
+        error = 'Bad URL: ' + url
+        raise OSError(error)
+    drive = comp[0][-1].upper()
+    components = comp[1].split('/')
+    path = drive + ':'
+    for comp in components:
+        if comp:
+            path = path + '\\' + urllib.parse.unquote(comp)
+    # Issue #11474 - handing url such as |c/|
+    if path.endswith(':') and url.endswith('/'):
+        path += '\\'
+    return path
+
+def pathname2url(p):
+    """OS-specific conversion from a file system path to a relative URL
+    of the 'file' scheme; not recommended for general use."""
+    # e.g.
+    #   C:\foo\bar\spam.foo
+    # becomes
+    #   ///C:/foo/bar/spam.foo
+    import urllib.parse
+    if not ':' in p:
+        # No drive specifier, just convert slashes and quote the name
+        if p[:2] == '\\\\':
+        # path is something like \\host\path\on\remote\host
+        # convert this to ////host/path/on/remote/host
+        # (notice doubling of slashes at the start of the path)
+            p = '\\\\' + p
+        components = p.split('\\')
+        return urllib.parse.quote('/'.join(components))
+    comp = p.split(':')
+    if len(comp) != 2 or len(comp[0]) > 1:
+        error = 'Bad path: ' + p
+        raise OSError(error)
+
+    drive = urllib.parse.quote(comp[0].upper())
+    components = comp[1].split('\\')
+    path = '///' + drive + ':'
+    for comp in components:
+        if comp:
+            path = path + '/' + urllib.parse.quote(comp)
+    return path
diff --git a/Lib/pydoc_data/__init__.py b/Lib/pydoc_data/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/Lib/pydoc_data/_pydoc.css b/Lib/pydoc_data/_pydoc.css
new file mode 100644
index 000000000..f036ef37a
--- /dev/null
+++ b/Lib/pydoc_data/_pydoc.css
@@ -0,0 +1,6 @@
+/*
+    CSS file for pydoc.
+
+    Contents of this file are subject to change without notice.
+
+*/
diff --git a/Lib/pydoc_data/topics.py b/Lib/pydoc_data/topics.py
new file mode 100644
index 000000000..e4c630580
--- /dev/null
+++ b/Lib/pydoc_data/topics.py
@@ -0,0 +1,13062 @@
+# -*- coding: utf-8 -*-
+# Autogenerated by Sphinx on Sun Dec 23 16:24:21 2018
+topics = {'assert': 'The "assert" statement\n'
+           '**********************\n'
+           '\n'
+           'Assert statements are a convenient way to insert debugging '
+           'assertions\n'
+           'into a program:\n'
+           '\n'
+           '   assert_stmt ::= "assert" expression ["," expression]\n'
+           '\n'
+           'The simple form, "assert expression", is equivalent to\n'
+           '\n'
+           '   if __debug__:\n'
+           '       if not expression: raise AssertionError\n'
+           '\n'
+           'The extended form, "assert expression1, expression2", is '
+           'equivalent to\n'
+           '\n'
+           '   if __debug__:\n'
+           '       if not expression1: raise AssertionError(expression2)\n'
+           '\n'
+           'These equivalences assume that "__debug__" and "AssertionError" '
+           'refer\n'
+           'to the built-in variables with those names.  In the current\n'
+           'implementation, the built-in variable "__debug__" is "True" under\n'
+           'normal circumstances, "False" when optimization is requested '
+           '(command\n'
+           'line option "-O").  The current code generator emits no code for '
+           'an\n'
+           'assert statement when optimization is requested at compile time.  '
+           'Note\n'
+           'that it is unnecessary to include the source code for the '
+           'expression\n'
+           'that failed in the error message; it will be displayed as part of '
+           'the\n'
+           'stack trace.\n'
+           '\n'
+           'Assignments to "__debug__" are illegal.  The value for the '
+           'built-in\n'
+           'variable is determined when the interpreter starts.\n',
+ 'assignment': 'Assignment statements\n'
+               '*********************\n'
+               '\n'
+               'Assignment statements are used to (re)bind names to values and '
+               'to\n'
+               'modify attributes or items of mutable objects:\n'
+               '\n'
+               '   assignment_stmt ::= (target_list "=")+ (starred_expression '
+               '| yield_expression)\n'
+               '   target_list     ::= target ("," target)* [","]\n'
+               '   target          ::= identifier\n'
+               '              | "(" [target_list] ")"\n'
+               '              | "[" [target_list] "]"\n'
+               '              | attributeref\n'
+               '              | subscription\n'
+               '              | slicing\n'
+               '              | "*" target\n'
+               '\n'
+               '(See section Primaries for the syntax definitions for '
+               '*attributeref*,\n'
+               '*subscription*, and *slicing*.)\n'
+               '\n'
+               'An assignment statement evaluates the expression list '
+               '(remember that\n'
+               'this can be a single expression or a comma-separated list, the '
+               'latter\n'
+               'yielding a tuple) and assigns the single resulting object to '
+               'each of\n'
+               'the target lists, from left to right.\n'
+               '\n'
+               'Assignment is defined recursively depending on the form of the '
+               'target\n'
+               '(list). When a target is part of a mutable object (an '
+               'attribute\n'
+               'reference, subscription or slicing), the mutable object must\n'
+               'ultimately perform the assignment and decide about its '
+               'validity, and\n'
+               'may raise an exception if the assignment is unacceptable.  The '
+               'rules\n'
+               'observed by various types and the exceptions raised are given '
+               'with the\n'
+               'definition of the object types (see section The standard type\n'
+               'hierarchy).\n'
+               '\n'
+               'Assignment of an object to a target list, optionally enclosed '
+               'in\n'
+               'parentheses or square brackets, is recursively defined as '
+               'follows.\n'
+               '\n'
+               '* If the target list is a single target with no trailing '
+               'comma,\n'
+               '  optionally in parentheses, the object is assigned to that '
+               'target.\n'
+               '\n'
+               '* Else: The object must be an iterable with the same number of '
+               'items\n'
+               '  as there are targets in the target list, and the items are '
+               'assigned,\n'
+               '  from left to right, to the corresponding targets.\n'
+               '\n'
+               '  * If the target list contains one target prefixed with an\n'
+               '    asterisk, called a “starred” target: The object must be '
+               'an\n'
+               '    iterable with at least as many items as there are targets '
+               'in the\n'
+               '    target list, minus one.  The first items of the iterable '
+               'are\n'
+               '    assigned, from left to right, to the targets before the '
+               'starred\n'
+               '    target.  The final items of the iterable are assigned to '
+               'the\n'
+               '    targets after the starred target.  A list of the remaining '
+               'items\n'
+               '    in the iterable is then assigned to the starred target '
+               '(the list\n'
+               '    can be empty).\n'
+               '\n'
+               '  * Else: The object must be an iterable with the same number '
+               'of\n'
+               '    items as there are targets in the target list, and the '
+               'items are\n'
+               '    assigned, from left to right, to the corresponding '
+               'targets.\n'
+               '\n'
+               'Assignment of an object to a single target is recursively '
+               'defined as\n'
+               'follows.\n'
+               '\n'
+               '* If the target is an identifier (name):\n'
+               '\n'
+               '  * If the name does not occur in a "global" or "nonlocal" '
+               'statement\n'
+               '    in the current code block: the name is bound to the object '
+               'in the\n'
+               '    current local namespace.\n'
+               '\n'
+               '  * Otherwise: the name is bound to the object in the global\n'
+               '    namespace or the outer namespace determined by '
+               '"nonlocal",\n'
+               '    respectively.\n'
+               '\n'
+               '  The name is rebound if it was already bound.  This may cause '
+               'the\n'
+               '  reference count for the object previously bound to the name '
+               'to reach\n'
+               '  zero, causing the object to be deallocated and its '
+               'destructor (if it\n'
+               '  has one) to be called.\n'
+               '\n'
+               '* If the target is an attribute reference: The primary '
+               'expression in\n'
+               '  the reference is evaluated.  It should yield an object with\n'
+               '  assignable attributes; if this is not the case, "TypeError" '
+               'is\n'
+               '  raised.  That object is then asked to assign the assigned '
+               'object to\n'
+               '  the given attribute; if it cannot perform the assignment, it '
+               'raises\n'
+               '  an exception (usually but not necessarily '
+               '"AttributeError").\n'
+               '\n'
+               '  Note: If the object is a class instance and the attribute '
+               'reference\n'
+               '  occurs on both sides of the assignment operator, the RHS '
+               'expression,\n'
+               '  "a.x" can access either an instance attribute or (if no '
+               'instance\n'
+               '  attribute exists) a class attribute.  The LHS target "a.x" '
+               'is always\n'
+               '  set as an instance attribute, creating it if necessary.  '
+               'Thus, the\n'
+               '  two occurrences of "a.x" do not necessarily refer to the '
+               'same\n'
+               '  attribute: if the RHS expression refers to a class '
+               'attribute, the\n'
+               '  LHS creates a new instance attribute as the target of the\n'
+               '  assignment:\n'
+               '\n'
+               '     class Cls:\n'
+               '         x = 3             # class variable\n'
+               '     inst = Cls()\n'
+               '     inst.x = inst.x + 1   # writes inst.x as 4 leaving Cls.x '
+               'as 3\n'
+               '\n'
+               '  This description does not necessarily apply to descriptor\n'
+               '  attributes, such as properties created with "property()".\n'
+               '\n'
+               '* If the target is a subscription: The primary expression in '
+               'the\n'
+               '  reference is evaluated.  It should yield either a mutable '
+               'sequence\n'
+               '  object (such as a list) or a mapping object (such as a '
+               'dictionary).\n'
+               '  Next, the subscript expression is evaluated.\n'
+               '\n'
+               '  If the primary is a mutable sequence object (such as a '
+               'list), the\n'
+               '  subscript must yield an integer.  If it is negative, the '
+               'sequence’s\n'
+               '  length is added to it.  The resulting value must be a '
+               'nonnegative\n'
+               '  integer less than the sequence’s length, and the sequence is '
+               'asked\n'
+               '  to assign the assigned object to its item with that index.  '
+               'If the\n'
+               '  index is out of range, "IndexError" is raised (assignment to '
+               'a\n'
+               '  subscripted sequence cannot add new items to a list).\n'
+               '\n'
+               '  If the primary is a mapping object (such as a dictionary), '
+               'the\n'
+               '  subscript must have a type compatible with the mapping’s key '
+               'type,\n'
+               '  and the mapping is then asked to create a key/datum pair '
+               'which maps\n'
+               '  the subscript to the assigned object.  This can either '
+               'replace an\n'
+               '  existing key/value pair with the same key value, or insert a '
+               'new\n'
+               '  key/value pair (if no key with the same value existed).\n'
+               '\n'
+               '  For user-defined objects, the "__setitem__()" method is '
+               'called with\n'
+               '  appropriate arguments.\n'
+               '\n'
+               '* If the target is a slicing: The primary expression in the\n'
+               '  reference is evaluated.  It should yield a mutable sequence '
+               'object\n'
+               '  (such as a list).  The assigned object should be a sequence '
+               'object\n'
+               '  of the same type.  Next, the lower and upper bound '
+               'expressions are\n'
+               '  evaluated, insofar they are present; defaults are zero and '
+               'the\n'
+               '  sequence’s length.  The bounds should evaluate to integers. '
+               'If\n'
+               '  either bound is negative, the sequence’s length is added to '
+               'it.  The\n'
+               '  resulting bounds are clipped to lie between zero and the '
+               'sequence’s\n'
+               '  length, inclusive.  Finally, the sequence object is asked to '
+               'replace\n'
+               '  the slice with the items of the assigned sequence.  The '
+               'length of\n'
+               '  the slice may be different from the length of the assigned '
+               'sequence,\n'
+               '  thus changing the length of the target sequence, if the '
+               'target\n'
+               '  sequence allows it.\n'
+               '\n'
+               '**CPython implementation detail:** In the current '
+               'implementation, the\n'
+               'syntax for targets is taken to be the same as for expressions, '
+               'and\n'
+               'invalid syntax is rejected during the code generation phase, '
+               'causing\n'
+               'less detailed error messages.\n'
+               '\n'
+               'Although the definition of assignment implies that overlaps '
+               'between\n'
+               'the left-hand side and the right-hand side are ‘simultaneous’ '
+               '(for\n'
+               'example "a, b = b, a" swaps two variables), overlaps *within* '
+               'the\n'
+               'collection of assigned-to variables occur left-to-right, '
+               'sometimes\n'
+               'resulting in confusion.  For instance, the following program '
+               'prints\n'
+               '"[0, 2]":\n'
+               '\n'
+               '   x = [0, 1]\n'
+               '   i = 0\n'
+               '   i, x[i] = 1, 2         # i is updated, then x[i] is '
+               'updated\n'
+               '   print(x)\n'
+               '\n'
+               'See also:\n'
+               '\n'
+               '  **PEP 3132** - Extended Iterable Unpacking\n'
+               '     The specification for the "*target" feature.\n'
+               '\n'
+               '\n'
+               'Augmented assignment statements\n'
+               '===============================\n'
+               '\n'
+               'Augmented assignment is the combination, in a single '
+               'statement, of a\n'
+               'binary operation and an assignment statement:\n'
+               '\n'
+               '   augmented_assignment_stmt ::= augtarget augop '
+               '(expression_list | yield_expression)\n'
+               '   augtarget                 ::= identifier | attributeref | '
+               'subscription | slicing\n'
+               '   augop                     ::= "+=" | "-=" | "*=" | "@=" | '
+               '"/=" | "//=" | "%=" | "**="\n'
+               '             | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
+               '\n'
+               '(See section Primaries for the syntax definitions of the last '
+               'three\n'
+               'symbols.)\n'
+               '\n'
+               'An augmented assignment evaluates the target (which, unlike '
+               'normal\n'
+               'assignment statements, cannot be an unpacking) and the '
+               'expression\n'
+               'list, performs the binary operation specific to the type of '
+               'assignment\n'
+               'on the two operands, and assigns the result to the original '
+               'target.\n'
+               'The target is only evaluated once.\n'
+               '\n'
+               'An augmented assignment expression like "x += 1" can be '
+               'rewritten as\n'
+               '"x = x + 1" to achieve a similar, but not exactly equal '
+               'effect. In the\n'
+               'augmented version, "x" is only evaluated once. Also, when '
+               'possible,\n'
+               'the actual operation is performed *in-place*, meaning that '
+               'rather than\n'
+               'creating a new object and assigning that to the target, the '
+               'old object\n'
+               'is modified instead.\n'
+               '\n'
+               'Unlike normal assignments, augmented assignments evaluate the '
+               'left-\n'
+               'hand side *before* evaluating the right-hand side.  For '
+               'example, "a[i]\n'
+               '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
+               'performs\n'
+               'the addition, and lastly, it writes the result back to '
+               '"a[i]".\n'
+               '\n'
+               'With the exception of assigning to tuples and multiple targets '
+               'in a\n'
+               'single statement, the assignment done by augmented assignment\n'
+               'statements is handled the same way as normal assignments. '
+               'Similarly,\n'
+               'with the exception of the possible *in-place* behavior, the '
+               'binary\n'
+               'operation performed by augmented assignment is the same as the '
+               'normal\n'
+               'binary operations.\n'
+               '\n'
+               'For targets which are attribute references, the same caveat '
+               'about\n'
+               'class and instance attributes applies as for regular '
+               'assignments.\n'
+               '\n'
+               '\n'
+               'Annotated assignment statements\n'
+               '===============================\n'
+               '\n'
+               'Annotation assignment is the combination, in a single '
+               'statement, of a\n'
+               'variable or attribute annotation and an optional assignment '
+               'statement:\n'
+               '\n'
+               '   annotated_assignment_stmt ::= augtarget ":" expression ["=" '
+               'expression]\n'
+               '\n'
+               'The difference from normal Assignment statements is that only '
+               'single\n'
+               'target and only single right hand side value is allowed.\n'
+               '\n'
+               'For simple names as assignment targets, if in class or module '
+               'scope,\n'
+               'the annotations are evaluated and stored in a special class or '
+               'module\n'
+               'attribute "__annotations__" that is a dictionary mapping from '
+               'variable\n'
+               'names (mangled if private) to evaluated annotations. This '
+               'attribute is\n'
+               'writable and is automatically created at the start of class or '
+               'module\n'
+               'body execution, if annotations are found statically.\n'
+               '\n'
+               'For expressions as assignment targets, the annotations are '
+               'evaluated\n'
+               'if in class or module scope, but not stored.\n'
+               '\n'
+               'If a name is annotated in a function scope, then this name is '
+               'local\n'
+               'for that scope. Annotations are never evaluated and stored in '
+               'function\n'
+               'scopes.\n'
+               '\n'
+               'If the right hand side is present, an annotated assignment '
+               'performs\n'
+               'the actual assignment before evaluating annotations (where\n'
+               'applicable). If the right hand side is not present for an '
+               'expression\n'
+               'target, then the interpreter evaluates the target except for '
+               'the last\n'
+               '"__setitem__()" or "__setattr__()" call.\n'
+               '\n'
+               'See also:\n'
+               '\n'
+               '  **PEP 526** - Syntax for Variable Annotations\n'
+               '     The proposal that added syntax for annotating the types '
+               'of\n'
+               '     variables (including class variables and instance '
+               'variables),\n'
+               '     instead of expressing them through comments.\n'
+               '\n'
+               '  **PEP 484** - Type hints\n'
+               '     The proposal that added the "typing" module to provide a '
+               'standard\n'
+               '     syntax for type annotations that can be used in static '
+               'analysis\n'
+               '     tools and IDEs.\n',
+ 'atom-identifiers': 'Identifiers (Names)\n'
+                     '*******************\n'
+                     '\n'
+                     'An identifier occurring as an atom is a name.  See '
+                     'section Identifiers\n'
+                     'and keywords for lexical definition and section Naming '
+                     'and binding for\n'
+                     'documentation of naming and binding.\n'
+                     '\n'
+                     'When the name is bound to an object, evaluation of the '
+                     'atom yields\n'
+                     'that object. When a name is not bound, an attempt to '
+                     'evaluate it\n'
+                     'raises a "NameError" exception.\n'
+                     '\n'
+                     '**Private name mangling:** When an identifier that '
+                     'textually occurs in\n'
+                     'a class definition begins with two or more underscore '
+                     'characters and\n'
+                     'does not end in two or more underscores, it is '
+                     'considered a *private\n'
+                     'name* of that class. Private names are transformed to a '
+                     'longer form\n'
+                     'before code is generated for them.  The transformation '
+                     'inserts the\n'
+                     'class name, with leading underscores removed and a '
+                     'single underscore\n'
+                     'inserted, in front of the name.  For example, the '
+                     'identifier "__spam"\n'
+                     'occurring in a class named "Ham" will be transformed to '
+                     '"_Ham__spam".\n'
+                     'This transformation is independent of the syntactical '
+                     'context in which\n'
+                     'the identifier is used.  If the transformed name is '
+                     'extremely long\n'
+                     '(longer than 255 characters), implementation defined '
+                     'truncation may\n'
+                     'happen. If the class name consists only of underscores, '
+                     'no\n'
+                     'transformation is done.\n',
+ 'atom-literals': 'Literals\n'
+                  '********\n'
+                  '\n'
+                  'Python supports string and bytes literals and various '
+                  'numeric\n'
+                  'literals:\n'
+                  '\n'
+                  '   literal ::= stringliteral | bytesliteral\n'
+                  '               | integer | floatnumber | imagnumber\n'
+                  '\n'
+                  'Evaluation of a literal yields an object of the given type '
+                  '(string,\n'
+                  'bytes, integer, floating point number, complex number) with '
+                  'the given\n'
+                  'value.  The value may be approximated in the case of '
+                  'floating point\n'
+                  'and imaginary (complex) literals.  See section Literals for '
+                  'details.\n'
+                  '\n'
+                  'All literals correspond to immutable data types, and hence '
+                  'the\n'
+                  'object’s identity is less important than its value.  '
+                  'Multiple\n'
+                  'evaluations of literals with the same value (either the '
+                  'same\n'
+                  'occurrence in the program text or a different occurrence) '
+                  'may obtain\n'
+                  'the same object or a different object with the same '
+                  'value.\n',
+ 'attribute-access': 'Customizing attribute access\n'
+                     '****************************\n'
+                     '\n'
+                     'The following methods can be defined to customize the '
+                     'meaning of\n'
+                     'attribute access (use of, assignment to, or deletion of '
+                     '"x.name") for\n'
+                     'class instances.\n'
+                     '\n'
+                     'object.__getattr__(self, name)\n'
+                     '\n'
+                     '   Called when the default attribute access fails with '
+                     'an\n'
+                     '   "AttributeError" (either "__getattribute__()" raises '
+                     'an\n'
+                     '   "AttributeError" because *name* is not an instance '
+                     'attribute or an\n'
+                     '   attribute in the class tree for "self"; or '
+                     '"__get__()" of a *name*\n'
+                     '   property raises "AttributeError").  This method '
+                     'should either\n'
+                     '   return the (computed) attribute value or raise an '
+                     '"AttributeError"\n'
+                     '   exception.\n'
+                     '\n'
+                     '   Note that if the attribute is found through the '
+                     'normal mechanism,\n'
+                     '   "__getattr__()" is not called.  (This is an '
+                     'intentional asymmetry\n'
+                     '   between "__getattr__()" and "__setattr__()".) This is '
+                     'done both for\n'
+                     '   efficiency reasons and because otherwise '
+                     '"__getattr__()" would have\n'
+                     '   no way to access other attributes of the instance.  '
+                     'Note that at\n'
+                     '   least for instance variables, you can fake total '
+                     'control by not\n'
+                     '   inserting any values in the instance attribute '
+                     'dictionary (but\n'
+                     '   instead inserting them in another object).  See the\n'
+                     '   "__getattribute__()" method below for a way to '
+                     'actually get total\n'
+                     '   control over attribute access.\n'
+                     '\n'
+                     'object.__getattribute__(self, name)\n'
+                     '\n'
+                     '   Called unconditionally to implement attribute '
+                     'accesses for\n'
+                     '   instances of the class. If the class also defines '
+                     '"__getattr__()",\n'
+                     '   the latter will not be called unless '
+                     '"__getattribute__()" either\n'
+                     '   calls it explicitly or raises an "AttributeError". '
+                     'This method\n'
+                     '   should return the (computed) attribute value or raise '
+                     'an\n'
+                     '   "AttributeError" exception. In order to avoid '
+                     'infinite recursion in\n'
+                     '   this method, its implementation should always call '
+                     'the base class\n'
+                     '   method with the same name to access any attributes it '
+                     'needs, for\n'
+                     '   example, "object.__getattribute__(self, name)".\n'
+                     '\n'
+                     '   Note: This method may still be bypassed when looking '
+                     'up special\n'
+                     '     methods as the result of implicit invocation via '
+                     'language syntax\n'
+                     '     or built-in functions. See Special method lookup.\n'
+                     '\n'
+                     'object.__setattr__(self, name, value)\n'
+                     '\n'
+                     '   Called when an attribute assignment is attempted.  '
+                     'This is called\n'
+                     '   instead of the normal mechanism (i.e. store the value '
+                     'in the\n'
+                     '   instance dictionary). *name* is the attribute name, '
+                     '*value* is the\n'
+                     '   value to be assigned to it.\n'
+                     '\n'
+                     '   If "__setattr__()" wants to assign to an instance '
+                     'attribute, it\n'
+                     '   should call the base class method with the same name, '
+                     'for example,\n'
+                     '   "object.__setattr__(self, name, value)".\n'
+                     '\n'
+                     'object.__delattr__(self, name)\n'
+                     '\n'
+                     '   Like "__setattr__()" but for attribute deletion '
+                     'instead of\n'
+                     '   assignment.  This should only be implemented if "del '
+                     'obj.name" is\n'
+                     '   meaningful for the object.\n'
+                     '\n'
+                     'object.__dir__(self)\n'
+                     '\n'
+                     '   Called when "dir()" is called on the object. A '
+                     'sequence must be\n'
+                     '   returned. "dir()" converts the returned sequence to a '
+                     'list and\n'
+                     '   sorts it.\n'
+                     '\n'
+                     '\n'
+                     'Customizing module attribute access\n'
+                     '===================================\n'
+                     '\n'
+                     'For a more fine grained customization of the module '
+                     'behavior (setting\n'
+                     'attributes, properties, etc.), one can set the '
+                     '"__class__" attribute\n'
+                     'of a module object to a subclass of "types.ModuleType". '
+                     'For example:\n'
+                     '\n'
+                     '   import sys\n'
+                     '   from types import ModuleType\n'
+                     '\n'
+                     '   class VerboseModule(ModuleType):\n'
+                     '       def __repr__(self):\n'
+                     "           return f'Verbose {self.__name__}'\n"
+                     '\n'
+                     '       def __setattr__(self, attr, value):\n'
+                     "           print(f'Setting {attr}...')\n"
+                     '           setattr(self, attr, value)\n'
+                     '\n'
+                     '   sys.modules[__name__].__class__ = VerboseModule\n'
+                     '\n'
+                     'Note: Setting module "__class__" only affects lookups '
+                     'made using the\n'
+                     '  attribute access syntax – directly accessing the '
+                     'module globals\n'
+                     '  (whether by code within the module, or via a reference '
+                     'to the\n'
+                     '  module’s globals dictionary) is unaffected.\n'
+                     '\n'
+                     'Changed in version 3.5: "__class__" module attribute is '
+                     'now writable.\n'
+                     '\n'
+                     '\n'
+                     'Implementing Descriptors\n'
+                     '========================\n'
+                     '\n'
+                     'The following methods only apply when an instance of the '
+                     'class\n'
+                     'containing the method (a so-called *descriptor* class) '
+                     'appears in an\n'
+                     '*owner* class (the descriptor must be in either the '
+                     'owner’s class\n'
+                     'dictionary or in the class dictionary for one of its '
+                     'parents).  In the\n'
+                     'examples below, “the attribute” refers to the attribute '
+                     'whose name is\n'
+                     'the key of the property in the owner class’ "__dict__".\n'
+                     '\n'
+                     'object.__get__(self, instance, owner)\n'
+                     '\n'
+                     '   Called to get the attribute of the owner class (class '
+                     'attribute\n'
+                     '   access) or of an instance of that class (instance '
+                     'attribute\n'
+                     '   access). *owner* is always the owner class, while '
+                     '*instance* is the\n'
+                     '   instance that the attribute was accessed through, or '
+                     '"None" when\n'
+                     '   the attribute is accessed through the *owner*.  This '
+                     'method should\n'
+                     '   return the (computed) attribute value or raise an '
+                     '"AttributeError"\n'
+                     '   exception.\n'
+                     '\n'
+                     'object.__set__(self, instance, value)\n'
+                     '\n'
+                     '   Called to set the attribute on an instance *instance* '
+                     'of the owner\n'
+                     '   class to a new value, *value*.\n'
+                     '\n'
+                     'object.__delete__(self, instance)\n'
+                     '\n'
+                     '   Called to delete the attribute on an instance '
+                     '*instance* of the\n'
+                     '   owner class.\n'
+                     '\n'
+                     'object.__set_name__(self, owner, name)\n'
+                     '\n'
+                     '   Called at the time the owning class *owner* is '
+                     'created. The\n'
+                     '   descriptor has been assigned to *name*.\n'
+                     '\n'
+                     '   New in version 3.6.\n'
+                     '\n'
+                     'The attribute "__objclass__" is interpreted by the '
+                     '"inspect" module as\n'
+                     'specifying the class where this object was defined '
+                     '(setting this\n'
+                     'appropriately can assist in runtime introspection of '
+                     'dynamic class\n'
+                     'attributes). For callables, it may indicate that an '
+                     'instance of the\n'
+                     'given type (or a subclass) is expected or required as '
+                     'the first\n'
+                     'positional argument (for example, CPython sets this '
+                     'attribute for\n'
+                     'unbound methods that are implemented in C).\n'
+                     '\n'
+                     '\n'
+                     'Invoking Descriptors\n'
+                     '====================\n'
+                     '\n'
+                     'In general, a descriptor is an object attribute with '
+                     '“binding\n'
+                     'behavior”, one whose attribute access has been '
+                     'overridden by methods\n'
+                     'in the descriptor protocol:  "__get__()", "__set__()", '
+                     'and\n'
+                     '"__delete__()". If any of those methods are defined for '
+                     'an object, it\n'
+                     'is said to be a descriptor.\n'
+                     '\n'
+                     'The default behavior for attribute access is to get, '
+                     'set, or delete\n'
+                     'the attribute from an object’s dictionary. For instance, '
+                     '"a.x" has a\n'
+                     'lookup chain starting with "a.__dict__[\'x\']", then\n'
+                     '"type(a).__dict__[\'x\']", and continuing through the '
+                     'base classes of\n'
+                     '"type(a)" excluding metaclasses.\n'
+                     '\n'
+                     'However, if the looked-up value is an object defining '
+                     'one of the\n'
+                     'descriptor methods, then Python may override the default '
+                     'behavior and\n'
+                     'invoke the descriptor method instead.  Where this occurs '
+                     'in the\n'
+                     'precedence chain depends on which descriptor methods '
+                     'were defined and\n'
+                     'how they were called.\n'
+                     '\n'
+                     'The starting point for descriptor invocation is a '
+                     'binding, "a.x". How\n'
+                     'the arguments are assembled depends on "a":\n'
+                     '\n'
+                     'Direct Call\n'
+                     '   The simplest and least common call is when user code '
+                     'directly\n'
+                     '   invokes a descriptor method:    "x.__get__(a)".\n'
+                     '\n'
+                     'Instance Binding\n'
+                     '   If binding to an object instance, "a.x" is '
+                     'transformed into the\n'
+                     '   call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n'
+                     '\n'
+                     'Class Binding\n'
+                     '   If binding to a class, "A.x" is transformed into the '
+                     'call:\n'
+                     '   "A.__dict__[\'x\'].__get__(None, A)".\n'
+                     '\n'
+                     'Super Binding\n'
+                     '   If "a" is an instance of "super", then the binding '
+                     '"super(B,\n'
+                     '   obj).m()" searches "obj.__class__.__mro__" for the '
+                     'base class "A"\n'
+                     '   immediately preceding "B" and then invokes the '
+                     'descriptor with the\n'
+                     '   call: "A.__dict__[\'m\'].__get__(obj, '
+                     'obj.__class__)".\n'
+                     '\n'
+                     'For instance bindings, the precedence of descriptor '
+                     'invocation depends\n'
+                     'on the which descriptor methods are defined.  A '
+                     'descriptor can define\n'
+                     'any combination of "__get__()", "__set__()" and '
+                     '"__delete__()".  If it\n'
+                     'does not define "__get__()", then accessing the '
+                     'attribute will return\n'
+                     'the descriptor object itself unless there is a value in '
+                     'the object’s\n'
+                     'instance dictionary.  If the descriptor defines '
+                     '"__set__()" and/or\n'
+                     '"__delete__()", it is a data descriptor; if it defines '
+                     'neither, it is\n'
+                     'a non-data descriptor.  Normally, data descriptors '
+                     'define both\n'
+                     '"__get__()" and "__set__()", while non-data descriptors '
+                     'have just the\n'
+                     '"__get__()" method.  Data descriptors with "__set__()" '
+                     'and "__get__()"\n'
+                     'defined always override a redefinition in an instance '
+                     'dictionary.  In\n'
+                     'contrast, non-data descriptors can be overridden by '
+                     'instances.\n'
+                     '\n'
+                     'Python methods (including "staticmethod()" and '
+                     '"classmethod()") are\n'
+                     'implemented as non-data descriptors.  Accordingly, '
+                     'instances can\n'
+                     'redefine and override methods.  This allows individual '
+                     'instances to\n'
+                     'acquire behaviors that differ from other instances of '
+                     'the same class.\n'
+                     '\n'
+                     'The "property()" function is implemented as a data '
+                     'descriptor.\n'
+                     'Accordingly, instances cannot override the behavior of a '
+                     'property.\n'
+                     '\n'
+                     '\n'
+                     '__slots__\n'
+                     '=========\n'
+                     '\n'
+                     '*__slots__* allow us to explicitly declare data members '
+                     '(like\n'
+                     'properties) and deny the creation of *__dict__* and '
+                     '*__weakref__*\n'
+                     '(unless explicitly declared in *__slots__* or available '
+                     'in a parent.)\n'
+                     '\n'
+                     'The space saved over using *__dict__* can be '
+                     'significant.\n'
+                     '\n'
+                     'object.__slots__\n'
+                     '\n'
+                     '   This class variable can be assigned a string, '
+                     'iterable, or sequence\n'
+                     '   of strings with variable names used by instances.  '
+                     '*__slots__*\n'
+                     '   reserves space for the declared variables and '
+                     'prevents the\n'
+                     '   automatic creation of *__dict__* and *__weakref__* '
+                     'for each\n'
+                     '   instance.\n'
+                     '\n'
+                     '\n'
+                     'Notes on using *__slots__*\n'
+                     '--------------------------\n'
+                     '\n'
+                     '* When inheriting from a class without *__slots__*, the '
+                     '*__dict__*\n'
+                     '  and *__weakref__* attribute of the instances will '
+                     'always be\n'
+                     '  accessible.\n'
+                     '\n'
+                     '* Without a *__dict__* variable, instances cannot be '
+                     'assigned new\n'
+                     '  variables not listed in the *__slots__* definition.  '
+                     'Attempts to\n'
+                     '  assign to an unlisted variable name raises '
+                     '"AttributeError". If\n'
+                     '  dynamic assignment of new variables is desired, then '
+                     'add\n'
+                     '  "\'__dict__\'" to the sequence of strings in the '
+                     '*__slots__*\n'
+                     '  declaration.\n'
+                     '\n'
+                     '* Without a *__weakref__* variable for each instance, '
+                     'classes\n'
+                     '  defining *__slots__* do not support weak references to '
+                     'its\n'
+                     '  instances. If weak reference support is needed, then '
+                     'add\n'
+                     '  "\'__weakref__\'" to the sequence of strings in the '
+                     '*__slots__*\n'
+                     '  declaration.\n'
+                     '\n'
+                     '* *__slots__* are implemented at the class level by '
+                     'creating\n'
+                     '  descriptors (Implementing Descriptors) for each '
+                     'variable name.  As a\n'
+                     '  result, class attributes cannot be used to set default '
+                     'values for\n'
+                     '  instance variables defined by *__slots__*; otherwise, '
+                     'the class\n'
+                     '  attribute would overwrite the descriptor assignment.\n'
+                     '\n'
+                     '* The action of a *__slots__* declaration is not limited '
+                     'to the\n'
+                     '  class where it is defined.  *__slots__* declared in '
+                     'parents are\n'
+                     '  available in child classes. However, child subclasses '
+                     'will get a\n'
+                     '  *__dict__* and *__weakref__* unless they also define '
+                     '*__slots__*\n'
+                     '  (which should only contain names of any *additional* '
+                     'slots).\n'
+                     '\n'
+                     '* If a class defines a slot also defined in a base '
+                     'class, the\n'
+                     '  instance variable defined by the base class slot is '
+                     'inaccessible\n'
+                     '  (except by retrieving its descriptor directly from the '
+                     'base class).\n'
+                     '  This renders the meaning of the program undefined.  In '
+                     'the future, a\n'
+                     '  check may be added to prevent this.\n'
+                     '\n'
+                     '* Nonempty *__slots__* does not work for classes derived '
+                     'from\n'
+                     '  “variable-length” built-in types such as "int", '
+                     '"bytes" and "tuple".\n'
+                     '\n'
+                     '* Any non-string iterable may be assigned to '
+                     '*__slots__*. Mappings\n'
+                     '  may also be used; however, in the future, special '
+                     'meaning may be\n'
+                     '  assigned to the values corresponding to each key.\n'
+                     '\n'
+                     '* *__class__* assignment works only if both classes have '
+                     'the same\n'
+                     '  *__slots__*.\n'
+                     '\n'
+                     '* Multiple inheritance with multiple slotted parent '
+                     'classes can be\n'
+                     '  used, but only one parent is allowed to have '
+                     'attributes created by\n'
+                     '  slots (the other bases must have empty slot layouts) - '
+                     'violations\n'
+                     '  raise "TypeError".\n',
+ 'attribute-references': 'Attribute references\n'
+                         '********************\n'
+                         '\n'
+                         'An attribute reference is a primary followed by a '
+                         'period and a name:\n'
+                         '\n'
+                         '   attributeref ::= primary "." identifier\n'
+                         '\n'
+                         'The primary must evaluate to an object of a type '
+                         'that supports\n'
+                         'attribute references, which most objects do.  This '
+                         'object is then\n'
+                         'asked to produce the attribute whose name is the '
+                         'identifier.  This\n'
+                         'production can be customized by overriding the '
+                         '"__getattr__()" method.\n'
+                         'If this attribute is not available, the exception '
+                         '"AttributeError" is\n'
+                         'raised.  Otherwise, the type and value of the object '
+                         'produced is\n'
+                         'determined by the object.  Multiple evaluations of '
+                         'the same attribute\n'
+                         'reference may yield different objects.\n',
+ 'augassign': 'Augmented assignment statements\n'
+              '*******************************\n'
+              '\n'
+              'Augmented assignment is the combination, in a single statement, '
+              'of a\n'
+              'binary operation and an assignment statement:\n'
+              '\n'
+              '   augmented_assignment_stmt ::= augtarget augop '
+              '(expression_list | yield_expression)\n'
+              '   augtarget                 ::= identifier | attributeref | '
+              'subscription | slicing\n'
+              '   augop                     ::= "+=" | "-=" | "*=" | "@=" | '
+              '"/=" | "//=" | "%=" | "**="\n'
+              '             | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
+              '\n'
+              '(See section Primaries for the syntax definitions of the last '
+              'three\n'
+              'symbols.)\n'
+              '\n'
+              'An augmented assignment evaluates the target (which, unlike '
+              'normal\n'
+              'assignment statements, cannot be an unpacking) and the '
+              'expression\n'
+              'list, performs the binary operation specific to the type of '
+              'assignment\n'
+              'on the two operands, and assigns the result to the original '
+              'target.\n'
+              'The target is only evaluated once.\n'
+              '\n'
+              'An augmented assignment expression like "x += 1" can be '
+              'rewritten as\n'
+              '"x = x + 1" to achieve a similar, but not exactly equal effect. '
+              'In the\n'
+              'augmented version, "x" is only evaluated once. Also, when '
+              'possible,\n'
+              'the actual operation is performed *in-place*, meaning that '
+              'rather than\n'
+              'creating a new object and assigning that to the target, the old '
+              'object\n'
+              'is modified instead.\n'
+              '\n'
+              'Unlike normal assignments, augmented assignments evaluate the '
+              'left-\n'
+              'hand side *before* evaluating the right-hand side.  For '
+              'example, "a[i]\n'
+              '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
+              'performs\n'
+              'the addition, and lastly, it writes the result back to "a[i]".\n'
+              '\n'
+              'With the exception of assigning to tuples and multiple targets '
+              'in a\n'
+              'single statement, the assignment done by augmented assignment\n'
+              'statements is handled the same way as normal assignments. '
+              'Similarly,\n'
+              'with the exception of the possible *in-place* behavior, the '
+              'binary\n'
+              'operation performed by augmented assignment is the same as the '
+              'normal\n'
+              'binary operations.\n'
+              '\n'
+              'For targets which are attribute references, the same caveat '
+              'about\n'
+              'class and instance attributes applies as for regular '
+              'assignments.\n',
+ 'binary': 'Binary arithmetic operations\n'
+           '****************************\n'
+           '\n'
+           'The binary arithmetic operations have the conventional priority\n'
+           'levels.  Note that some of these operations also apply to certain '
+           'non-\n'
+           'numeric types.  Apart from the power operator, there are only two\n'
+           'levels, one for multiplicative operators and one for additive\n'
+           'operators:\n'
+           '\n'
+           '   m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@" m_expr |\n'
+           '              m_expr "//" u_expr | m_expr "/" u_expr |\n'
+           '              m_expr "%" u_expr\n'
+           '   a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr\n'
+           '\n'
+           'The "*" (multiplication) operator yields the product of its '
+           'arguments.\n'
+           'The arguments must either both be numbers, or one argument must be '
+           'an\n'
+           'integer and the other must be a sequence. In the former case, the\n'
+           'numbers are converted to a common type and then multiplied '
+           'together.\n'
+           'In the latter case, sequence repetition is performed; a negative\n'
+           'repetition factor yields an empty sequence.\n'
+           '\n'
+           'The "@" (at) operator is intended to be used for matrix\n'
+           'multiplication.  No builtin Python types implement this operator.\n'
+           '\n'
+           'New in version 3.5.\n'
+           '\n'
+           'The "/" (division) and "//" (floor division) operators yield the\n'
+           'quotient of their arguments.  The numeric arguments are first\n'
+           'converted to a common type. Division of integers yields a float, '
+           'while\n'
+           'floor division of integers results in an integer; the result is '
+           'that\n'
+           'of mathematical division with the ‘floor’ function applied to the\n'
+           'result.  Division by zero raises the "ZeroDivisionError" '
+           'exception.\n'
+           '\n'
+           'The "%" (modulo) operator yields the remainder from the division '
+           'of\n'
+           'the first argument by the second.  The numeric arguments are '
+           'first\n'
+           'converted to a common type.  A zero right argument raises the\n'
+           '"ZeroDivisionError" exception.  The arguments may be floating '
+           'point\n'
+           'numbers, e.g., "3.14%0.7" equals "0.34" (since "3.14" equals '
+           '"4*0.7 +\n'
+           '0.34".)  The modulo operator always yields a result with the same '
+           'sign\n'
+           'as its second operand (or zero); the absolute value of the result '
+           'is\n'
+           'strictly smaller than the absolute value of the second operand '
+           '[1].\n'
+           '\n'
+           'The floor division and modulo operators are connected by the '
+           'following\n'
+           'identity: "x == (x//y)*y + (x%y)".  Floor division and modulo are '
+           'also\n'
+           'connected with the built-in function "divmod()": "divmod(x, y) ==\n'
+           '(x//y, x%y)". [2].\n'
+           '\n'
+           'In addition to performing the modulo operation on numbers, the '
+           '"%"\n'
+           'operator is also overloaded by string objects to perform '
+           'old-style\n'
+           'string formatting (also known as interpolation).  The syntax for\n'
+           'string formatting is described in the Python Library Reference,\n'
+           'section printf-style String Formatting.\n'
+           '\n'
+           'The floor division operator, the modulo operator, and the '
+           '"divmod()"\n'
+           'function are not defined for complex numbers.  Instead, convert to '
+           'a\n'
+           'floating point number using the "abs()" function if appropriate.\n'
+           '\n'
+           'The "+" (addition) operator yields the sum of its arguments.  The\n'
+           'arguments must either both be numbers or both be sequences of the '
+           'same\n'
+           'type.  In the former case, the numbers are converted to a common '
+           'type\n'
+           'and then added together. In the latter case, the sequences are\n'
+           'concatenated.\n'
+           '\n'
+           'The "-" (subtraction) operator yields the difference of its '
+           'arguments.\n'
+           'The numeric arguments are first converted to a common type.\n',
+ 'bitwise': 'Binary bitwise operations\n'
+            '*************************\n'
+            '\n'
+            'Each of the three bitwise operations has a different priority '
+            'level:\n'
+            '\n'
+            '   and_expr ::= shift_expr | and_expr "&" shift_expr\n'
+            '   xor_expr ::= and_expr | xor_expr "^" and_expr\n'
+            '   or_expr  ::= xor_expr | or_expr "|" xor_expr\n'
+            '\n'
+            'The "&" operator yields the bitwise AND of its arguments, which '
+            'must\n'
+            'be integers.\n'
+            '\n'
+            'The "^" operator yields the bitwise XOR (exclusive OR) of its\n'
+            'arguments, which must be integers.\n'
+            '\n'
+            'The "|" operator yields the bitwise (inclusive) OR of its '
+            'arguments,\n'
+            'which must be integers.\n',
+ 'bltin-code-objects': 'Code Objects\n'
+                       '************\n'
+                       '\n'
+                       'Code objects are used by the implementation to '
+                       'represent “pseudo-\n'
+                       'compiled” executable Python code such as a function '
+                       'body. They differ\n'
+                       'from function objects because they don’t contain a '
+                       'reference to their\n'
+                       'global execution environment.  Code objects are '
+                       'returned by the built-\n'
+                       'in "compile()" function and can be extracted from '
+                       'function objects\n'
+                       'through their "__code__" attribute. See also the '
+                       '"code" module.\n'
+                       '\n'
+                       'A code object can be executed or evaluated by passing '
+                       'it (instead of a\n'
+                       'source string) to the "exec()" or "eval()"  built-in '
+                       'functions.\n'
+                       '\n'
+                       'See The standard type hierarchy for more '
+                       'information.\n',
+ 'bltin-ellipsis-object': 'The Ellipsis Object\n'
+                          '*******************\n'
+                          '\n'
+                          'This object is commonly used by slicing (see '
+                          'Slicings).  It supports\n'
+                          'no special operations.  There is exactly one '
+                          'ellipsis object, named\n'
+                          '"Ellipsis" (a built-in name).  "type(Ellipsis)()" '
+                          'produces the\n'
+                          '"Ellipsis" singleton.\n'
+                          '\n'
+                          'It is written as "Ellipsis" or "...".\n',
+ 'bltin-null-object': 'The Null Object\n'
+                      '***************\n'
+                      '\n'
+                      'This object is returned by functions that don’t '
+                      'explicitly return a\n'
+                      'value.  It supports no special operations.  There is '
+                      'exactly one null\n'
+                      'object, named "None" (a built-in name).  "type(None)()" '
+                      'produces the\n'
+                      'same singleton.\n'
+                      '\n'
+                      'It is written as "None".\n',
+ 'bltin-type-objects': 'Type Objects\n'
+                       '************\n'
+                       '\n'
+                       'Type objects represent the various object types.  An '
+                       'object’s type is\n'
+                       'accessed by the built-in function "type()".  There are '
+                       'no special\n'
+                       'operations on types.  The standard module "types" '
+                       'defines names for\n'
+                       'all standard built-in types.\n'
+                       '\n'
+                       'Types are written like this: "<class \'int\'>".\n',
+ 'booleans': 'Boolean operations\n'
+             '******************\n'
+             '\n'
+             '   or_test  ::= and_test | or_test "or" and_test\n'
+             '   and_test ::= not_test | and_test "and" not_test\n'
+             '   not_test ::= comparison | "not" not_test\n'
+             '\n'
+             'In the context of Boolean operations, and also when expressions '
+             'are\n'
+             'used by control flow statements, the following values are '
+             'interpreted\n'
+             'as false: "False", "None", numeric zero of all types, and empty\n'
+             'strings and containers (including strings, tuples, lists,\n'
+             'dictionaries, sets and frozensets).  All other values are '
+             'interpreted\n'
+             'as true.  User-defined objects can customize their truth value '
+             'by\n'
+             'providing a "__bool__()" method.\n'
+             '\n'
+             'The operator "not" yields "True" if its argument is false, '
+             '"False"\n'
+             'otherwise.\n'
+             '\n'
+             'The expression "x and y" first evaluates *x*; if *x* is false, '
+             'its\n'
+             'value is returned; otherwise, *y* is evaluated and the resulting '
+             'value\n'
+             'is returned.\n'
+             '\n'
+             'The expression "x or y" first evaluates *x*; if *x* is true, its '
+             'value\n'
+             'is returned; otherwise, *y* is evaluated and the resulting value '
+             'is\n'
+             'returned.\n'
+             '\n'
+             'Note that neither "and" nor "or" restrict the value and type '
+             'they\n'
+             'return to "False" and "True", but rather return the last '
+             'evaluated\n'
+             'argument.  This is sometimes useful, e.g., if "s" is a string '
+             'that\n'
+             'should be replaced by a default value if it is empty, the '
+             'expression\n'
+             '"s or \'foo\'" yields the desired value.  Because "not" has to '
+             'create a\n'
+             'new value, it returns a boolean value regardless of the type of '
+             'its\n'
+             'argument (for example, "not \'foo\'" produces "False" rather '
+             'than "\'\'".)\n',
+ 'break': 'The "break" statement\n'
+          '*********************\n'
+          '\n'
+          '   break_stmt ::= "break"\n'
+          '\n'
+          '"break" may only occur syntactically nested in a "for" or "while"\n'
+          'loop, but not nested in a function or class definition within that\n'
+          'loop.\n'
+          '\n'
+          'It terminates the nearest enclosing loop, skipping the optional '
+          '"else"\n'
+          'clause if the loop has one.\n'
+          '\n'
+          'If a "for" loop is terminated by "break", the loop control target\n'
+          'keeps its current value.\n'
+          '\n'
+          'When "break" passes control out of a "try" statement with a '
+          '"finally"\n'
+          'clause, that "finally" clause is executed before really leaving '
+          'the\n'
+          'loop.\n',
+ 'callable-types': 'Emulating callable objects\n'
+                   '**************************\n'
+                   '\n'
+                   'object.__call__(self[, args...])\n'
+                   '\n'
+                   '   Called when the instance is “called” as a function; if '
+                   'this method\n'
+                   '   is defined, "x(arg1, arg2, ...)" is a shorthand for\n'
+                   '   "x.__call__(arg1, arg2, ...)".\n',
+ 'calls': 'Calls\n'
+          '*****\n'
+          '\n'
+          'A call calls a callable object (e.g., a *function*) with a '
+          'possibly\n'
+          'empty series of *arguments*:\n'
+          '\n'
+          '   call                 ::= primary "(" [argument_list [","] | '
+          'comprehension] ")"\n'
+          '   argument_list        ::= positional_arguments ["," '
+          'starred_and_keywords]\n'
+          '                       ["," keywords_arguments]\n'
+          '                     | starred_and_keywords ["," '
+          'keywords_arguments]\n'
+          '                     | keywords_arguments\n'
+          '   positional_arguments ::= ["*"] expression ("," ["*"] '
+          'expression)*\n'
+          '   starred_and_keywords ::= ("*" expression | keyword_item)\n'
+          '                            ("," "*" expression | "," '
+          'keyword_item)*\n'
+          '   keywords_arguments   ::= (keyword_item | "**" expression)\n'
+          '                          ("," keyword_item | "," "**" '
+          'expression)*\n'
+          '   keyword_item         ::= identifier "=" expression\n'
+          '\n'
+          'An optional trailing comma may be present after the positional and\n'
+          'keyword arguments but does not affect the semantics.\n'
+          '\n'
+          'The primary must evaluate to a callable object (user-defined\n'
+          'functions, built-in functions, methods of built-in objects, class\n'
+          'objects, methods of class instances, and all objects having a\n'
+          '"__call__()" method are callable).  All argument expressions are\n'
+          'evaluated before the call is attempted.  Please refer to section\n'
+          'Function definitions for the syntax of formal *parameter* lists.\n'
+          '\n'
+          'If keyword arguments are present, they are first converted to\n'
+          'positional arguments, as follows.  First, a list of unfilled slots '
+          'is\n'
+          'created for the formal parameters.  If there are N positional\n'
+          'arguments, they are placed in the first N slots.  Next, for each\n'
+          'keyword argument, the identifier is used to determine the\n'
+          'corresponding slot (if the identifier is the same as the first '
+          'formal\n'
+          'parameter name, the first slot is used, and so on).  If the slot '
+          'is\n'
+          'already filled, a "TypeError" exception is raised. Otherwise, the\n'
+          'value of the argument is placed in the slot, filling it (even if '
+          'the\n'
+          'expression is "None", it fills the slot).  When all arguments have\n'
+          'been processed, the slots that are still unfilled are filled with '
+          'the\n'
+          'corresponding default value from the function definition.  '
+          '(Default\n'
+          'values are calculated, once, when the function is defined; thus, a\n'
+          'mutable object such as a list or dictionary used as default value '
+          'will\n'
+          'be shared by all calls that don’t specify an argument value for '
+          'the\n'
+          'corresponding slot; this should usually be avoided.)  If there are '
+          'any\n'
+          'unfilled slots for which no default value is specified, a '
+          '"TypeError"\n'
+          'exception is raised.  Otherwise, the list of filled slots is used '
+          'as\n'
+          'the argument list for the call.\n'
+          '\n'
+          '**CPython implementation detail:** An implementation may provide\n'
+          'built-in functions whose positional parameters do not have names, '
+          'even\n'
+          'if they are ‘named’ for the purpose of documentation, and which\n'
+          'therefore cannot be supplied by keyword.  In CPython, this is the '
+          'case\n'
+          'for functions implemented in C that use "PyArg_ParseTuple()" to '
+          'parse\n'
+          'their arguments.\n'
+          '\n'
+          'If there are more positional arguments than there are formal '
+          'parameter\n'
+          'slots, a "TypeError" exception is raised, unless a formal '
+          'parameter\n'
+          'using the syntax "*identifier" is present; in this case, that '
+          'formal\n'
+          'parameter receives a tuple containing the excess positional '
+          'arguments\n'
+          '(or an empty tuple if there were no excess positional arguments).\n'
+          '\n'
+          'If any keyword argument does not correspond to a formal parameter\n'
+          'name, a "TypeError" exception is raised, unless a formal parameter\n'
+          'using the syntax "**identifier" is present; in this case, that '
+          'formal\n'
+          'parameter receives a dictionary containing the excess keyword\n'
+          'arguments (using the keywords as keys and the argument values as\n'
+          'corresponding values), or a (new) empty dictionary if there were '
+          'no\n'
+          'excess keyword arguments.\n'
+          '\n'
+          'If the syntax "*expression" appears in the function call, '
+          '"expression"\n'
+          'must evaluate to an *iterable*.  Elements from these iterables are\n'
+          'treated as if they were additional positional arguments.  For the '
+          'call\n'
+          '"f(x1, x2, *y, x3, x4)", if *y* evaluates to a sequence *y1*, …, '
+          '*yM*,\n'
+          'this is equivalent to a call with M+4 positional arguments *x1*, '
+          '*x2*,\n'
+          '*y1*, …, *yM*, *x3*, *x4*.\n'
+          '\n'
+          'A consequence of this is that although the "*expression" syntax '
+          'may\n'
+          'appear *after* explicit keyword arguments, it is processed '
+          '*before*\n'
+          'the keyword arguments (and any "**expression" arguments – see '
+          'below).\n'
+          'So:\n'
+          '\n'
+          '   >>> def f(a, b):\n'
+          '   ...     print(a, b)\n'
+          '   ...\n'
+          '   >>> f(b=1, *(2,))\n'
+          '   2 1\n'
+          '   >>> f(a=1, *(2,))\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 1, in <module>\n'
+          "   TypeError: f() got multiple values for keyword argument 'a'\n"
+          '   >>> f(1, *(2,))\n'
+          '   1 2\n'
+          '\n'
+          'It is unusual for both keyword arguments and the "*expression" '
+          'syntax\n'
+          'to be used in the same call, so in practice this confusion does '
+          'not\n'
+          'arise.\n'
+          '\n'
+          'If the syntax "**expression" appears in the function call,\n'
+          '"expression" must evaluate to a *mapping*, the contents of which '
+          'are\n'
+          'treated as additional keyword arguments.  If a keyword is already\n'
+          'present (as an explicit keyword argument, or from another '
+          'unpacking),\n'
+          'a "TypeError" exception is raised.\n'
+          '\n'
+          'Formal parameters using the syntax "*identifier" or "**identifier"\n'
+          'cannot be used as positional argument slots or as keyword argument\n'
+          'names.\n'
+          '\n'
+          'Changed in version 3.5: Function calls accept any number of "*" '
+          'and\n'
+          '"**" unpackings, positional arguments may follow iterable '
+          'unpackings\n'
+          '("*"), and keyword arguments may follow dictionary unpackings '
+          '("**").\n'
+          'Originally proposed by **PEP 448**.\n'
+          '\n'
+          'A call always returns some value, possibly "None", unless it raises '
+          'an\n'
+          'exception.  How this value is computed depends on the type of the\n'
+          'callable object.\n'
+          '\n'
+          'If it is—\n'
+          '\n'
+          'a user-defined function:\n'
+          '   The code block for the function is executed, passing it the\n'
+          '   argument list.  The first thing the code block will do is bind '
+          'the\n'
+          '   formal parameters to the arguments; this is described in '
+          'section\n'
+          '   Function definitions.  When the code block executes a "return"\n'
+          '   statement, this specifies the return value of the function '
+          'call.\n'
+          '\n'
+          'a built-in function or method:\n'
+          '   The result is up to the interpreter; see Built-in Functions for '
+          'the\n'
+          '   descriptions of built-in functions and methods.\n'
+          '\n'
+          'a class object:\n'
+          '   A new instance of that class is returned.\n'
+          '\n'
+          'a class instance method:\n'
+          '   The corresponding user-defined function is called, with an '
+          'argument\n'
+          '   list that is one longer than the argument list of the call: the\n'
+          '   instance becomes the first argument.\n'
+          '\n'
+          'a class instance:\n'
+          '   The class must define a "__call__()" method; the effect is then '
+          'the\n'
+          '   same as if that method was called.\n',
+ 'class': 'Class definitions\n'
+          '*****************\n'
+          '\n'
+          'A class definition defines a class object (see section The '
+          'standard\n'
+          'type hierarchy):\n'
+          '\n'
+          '   classdef    ::= [decorators] "class" classname [inheritance] ":" '
+          'suite\n'
+          '   inheritance ::= "(" [argument_list] ")"\n'
+          '   classname   ::= identifier\n'
+          '\n'
+          'A class definition is an executable statement.  The inheritance '
+          'list\n'
+          'usually gives a list of base classes (see Metaclasses for more\n'
+          'advanced uses), so each item in the list should evaluate to a '
+          'class\n'
+          'object which allows subclassing.  Classes without an inheritance '
+          'list\n'
+          'inherit, by default, from the base class "object"; hence,\n'
+          '\n'
+          '   class Foo:\n'
+          '       pass\n'
+          '\n'
+          'is equivalent to\n'
+          '\n'
+          '   class Foo(object):\n'
+          '       pass\n'
+          '\n'
+          'The class’s suite is then executed in a new execution frame (see\n'
+          'Naming and binding), using a newly created local namespace and the\n'
+          'original global namespace. (Usually, the suite contains mostly\n'
+          'function definitions.)  When the class’s suite finishes execution, '
+          'its\n'
+          'execution frame is discarded but its local namespace is saved. [3] '
+          'A\n'
+          'class object is then created using the inheritance list for the '
+          'base\n'
+          'classes and the saved local namespace for the attribute '
+          'dictionary.\n'
+          'The class name is bound to this class object in the original local\n'
+          'namespace.\n'
+          '\n'
+          'The order in which attributes are defined in the class body is\n'
+          'preserved in the new class’s "__dict__".  Note that this is '
+          'reliable\n'
+          'only right after the class is created and only for classes that '
+          'were\n'
+          'defined using the definition syntax.\n'
+          '\n'
+          'Class creation can be customized heavily using metaclasses.\n'
+          '\n'
+          'Classes can also be decorated: just like when decorating '
+          'functions,\n'
+          '\n'
+          '   @f1(arg)\n'
+          '   @f2\n'
+          '   class Foo: pass\n'
+          '\n'
+          'is roughly equivalent to\n'
+          '\n'
+          '   class Foo: pass\n'
+          '   Foo = f1(arg)(f2(Foo))\n'
+          '\n'
+          'The evaluation rules for the decorator expressions are the same as '
+          'for\n'
+          'function decorators.  The result is then bound to the class name.\n'
+          '\n'
+          '**Programmer’s note:** Variables defined in the class definition '
+          'are\n'
+          'class attributes; they are shared by instances.  Instance '
+          'attributes\n'
+          'can be set in a method with "self.name = value".  Both class and\n'
+          'instance attributes are accessible through the notation '
+          '“"self.name"”,\n'
+          'and an instance attribute hides a class attribute with the same '
+          'name\n'
+          'when accessed in this way.  Class attributes can be used as '
+          'defaults\n'
+          'for instance attributes, but using mutable values there can lead '
+          'to\n'
+          'unexpected results.  Descriptors can be used to create instance\n'
+          'variables with different implementation details.\n'
+          '\n'
+          'See also:\n'
+          '\n'
+          '  **PEP 3115** - Metaclasses in Python 3000\n'
+          '     The proposal that changed the declaration of metaclasses to '
+          'the\n'
+          '     current syntax, and the semantics for how classes with\n'
+          '     metaclasses are constructed.\n'
+          '\n'
+          '  **PEP 3129** - Class Decorators\n'
+          '     The proposal that added class decorators.  Function and '
+          'method\n'
+          '     decorators were introduced in **PEP 318**.\n',
+ 'comparisons': 'Comparisons\n'
+                '***********\n'
+                '\n'
+                'Unlike C, all comparison operations in Python have the same '
+                'priority,\n'
+                'which is lower than that of any arithmetic, shifting or '
+                'bitwise\n'
+                'operation.  Also unlike C, expressions like "a < b < c" have '
+                'the\n'
+                'interpretation that is conventional in mathematics:\n'
+                '\n'
+                '   comparison    ::= or_expr (comp_operator or_expr)*\n'
+                '   comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "!="\n'
+                '                     | "is" ["not"] | ["not"] "in"\n'
+                '\n'
+                'Comparisons yield boolean values: "True" or "False".\n'
+                '\n'
+                'Comparisons can be chained arbitrarily, e.g., "x < y <= z" '
+                'is\n'
+                'equivalent to "x < y and y <= z", except that "y" is '
+                'evaluated only\n'
+                'once (but in both cases "z" is not evaluated at all when "x < '
+                'y" is\n'
+                'found to be false).\n'
+                '\n'
+                'Formally, if *a*, *b*, *c*, …, *y*, *z* are expressions and '
+                '*op1*,\n'
+                '*op2*, …, *opN* are comparison operators, then "a op1 b op2 c '
+                '... y\n'
+                'opN z" is equivalent to "a op1 b and b op2 c and ... y opN '
+                'z", except\n'
+                'that each expression is evaluated at most once.\n'
+                '\n'
+                'Note that "a op1 b op2 c" doesn’t imply any kind of '
+                'comparison between\n'
+                '*a* and *c*, so that, e.g., "x < y > z" is perfectly legal '
+                '(though\n'
+                'perhaps not pretty).\n'
+                '\n'
+                '\n'
+                'Value comparisons\n'
+                '=================\n'
+                '\n'
+                'The operators "<", ">", "==", ">=", "<=", and "!=" compare '
+                'the values\n'
+                'of two objects.  The objects do not need to have the same '
+                'type.\n'
+                '\n'
+                'Chapter Objects, values and types states that objects have a '
+                'value (in\n'
+                'addition to type and identity).  The value of an object is a '
+                'rather\n'
+                'abstract notion in Python: For example, there is no canonical '
+                'access\n'
+                'method for an object’s value.  Also, there is no requirement '
+                'that the\n'
+                'value of an object should be constructed in a particular way, '
+                'e.g.\n'
+                'comprised of all its data attributes. Comparison operators '
+                'implement a\n'
+                'particular notion of what the value of an object is.  One can '
+                'think of\n'
+                'them as defining the value of an object indirectly, by means '
+                'of their\n'
+                'comparison implementation.\n'
+                '\n'
+                'Because all types are (direct or indirect) subtypes of '
+                '"object", they\n'
+                'inherit the default comparison behavior from "object".  Types '
+                'can\n'
+                'customize their comparison behavior by implementing *rich '
+                'comparison\n'
+                'methods* like "__lt__()", described in Basic customization.\n'
+                '\n'
+                'The default behavior for equality comparison ("==" and "!=") '
+                'is based\n'
+                'on the identity of the objects.  Hence, equality comparison '
+                'of\n'
+                'instances with the same identity results in equality, and '
+                'equality\n'
+                'comparison of instances with different identities results in\n'
+                'inequality.  A motivation for this default behavior is the '
+                'desire that\n'
+                'all objects should be reflexive (i.e. "x is y" implies "x == '
+                'y").\n'
+                '\n'
+                'A default order comparison ("<", ">", "<=", and ">=") is not '
+                'provided;\n'
+                'an attempt raises "TypeError".  A motivation for this default '
+                'behavior\n'
+                'is the lack of a similar invariant as for equality.\n'
+                '\n'
+                'The behavior of the default equality comparison, that '
+                'instances with\n'
+                'different identities are always unequal, may be in contrast '
+                'to what\n'
+                'types will need that have a sensible definition of object '
+                'value and\n'
+                'value-based equality.  Such types will need to customize '
+                'their\n'
+                'comparison behavior, and in fact, a number of built-in types '
+                'have done\n'
+                'that.\n'
+                '\n'
+                'The following list describes the comparison behavior of the '
+                'most\n'
+                'important built-in types.\n'
+                '\n'
+                '* Numbers of built-in numeric types (Numeric Types — int, '
+                'float,\n'
+                '  complex) and of the standard library types '
+                '"fractions.Fraction" and\n'
+                '  "decimal.Decimal" can be compared within and across their '
+                'types,\n'
+                '  with the restriction that complex numbers do not support '
+                'order\n'
+                '  comparison.  Within the limits of the types involved, they '
+                'compare\n'
+                '  mathematically (algorithmically) correct without loss of '
+                'precision.\n'
+                '\n'
+                '  The not-a-number values "float(\'NaN\')" and '
+                '"Decimal(\'NaN\')" are\n'
+                '  special.  They are identical to themselves ("x is x" is '
+                'true) but\n'
+                '  are not equal to themselves ("x == x" is false).  '
+                'Additionally,\n'
+                '  comparing any number to a not-a-number value will return '
+                '"False".\n'
+                '  For example, both "3 < float(\'NaN\')" and "float(\'NaN\') '
+                '< 3" will\n'
+                '  return "False".\n'
+                '\n'
+                '* Binary sequences (instances of "bytes" or "bytearray") can '
+                'be\n'
+                '  compared within and across their types.  They compare\n'
+                '  lexicographically using the numeric values of their '
+                'elements.\n'
+                '\n'
+                '* Strings (instances of "str") compare lexicographically '
+                'using the\n'
+                '  numerical Unicode code points (the result of the built-in '
+                'function\n'
+                '  "ord()") of their characters. [3]\n'
+                '\n'
+                '  Strings and binary sequences cannot be directly compared.\n'
+                '\n'
+                '* Sequences (instances of "tuple", "list", or "range") can '
+                'be\n'
+                '  compared only within each of their types, with the '
+                'restriction that\n'
+                '  ranges do not support order comparison.  Equality '
+                'comparison across\n'
+                '  these types results in inequality, and ordering comparison '
+                'across\n'
+                '  these types raises "TypeError".\n'
+                '\n'
+                '  Sequences compare lexicographically using comparison of\n'
+                '  corresponding elements, whereby reflexivity of the elements '
+                'is\n'
+                '  enforced.\n'
+                '\n'
+                '  In enforcing reflexivity of elements, the comparison of '
+                'collections\n'
+                '  assumes that for a collection element "x", "x == x" is '
+                'always true.\n'
+                '  Based on that assumption, element identity is compared '
+                'first, and\n'
+                '  element comparison is performed only for distinct '
+                'elements.  This\n'
+                '  approach yields the same result as a strict element '
+                'comparison\n'
+                '  would, if the compared elements are reflexive.  For '
+                'non-reflexive\n'
+                '  elements, the result is different than for strict element\n'
+                '  comparison, and may be surprising:  The non-reflexive '
+                'not-a-number\n'
+                '  values for example result in the following comparison '
+                'behavior when\n'
+                '  used in a list:\n'
+                '\n'
+                "     >>> nan = float('NaN')\n"
+                '     >>> nan is nan\n'
+                '     True\n'
+                '     >>> nan == nan\n'
+                '     False                 <-- the defined non-reflexive '
+                'behavior of NaN\n'
+                '     >>> [nan] == [nan]\n'
+                '     True                  <-- list enforces reflexivity and '
+                'tests identity first\n'
+                '\n'
+                '  Lexicographical comparison between built-in collections '
+                'works as\n'
+                '  follows:\n'
+                '\n'
+                '  * For two collections to compare equal, they must be of the '
+                'same\n'
+                '    type, have the same length, and each pair of '
+                'corresponding\n'
+                '    elements must compare equal (for example, "[1,2] == '
+                '(1,2)" is\n'
+                '    false because the type is not the same).\n'
+                '\n'
+                '  * Collections that support order comparison are ordered the '
+                'same\n'
+                '    as their first unequal elements (for example, "[1,2,x] <= '
+                '[1,2,y]"\n'
+                '    has the same value as "x <= y").  If a corresponding '
+                'element does\n'
+                '    not exist, the shorter collection is ordered first (for '
+                'example,\n'
+                '    "[1,2] < [1,2,3]" is true).\n'
+                '\n'
+                '* Mappings (instances of "dict") compare equal if and only if '
+                'they\n'
+                '  have equal *(key, value)* pairs. Equality comparison of the '
+                'keys and\n'
+                '  values enforces reflexivity.\n'
+                '\n'
+                '  Order comparisons ("<", ">", "<=", and ">=") raise '
+                '"TypeError".\n'
+                '\n'
+                '* Sets (instances of "set" or "frozenset") can be compared '
+                'within\n'
+                '  and across their types.\n'
+                '\n'
+                '  They define order comparison operators to mean subset and '
+                'superset\n'
+                '  tests.  Those relations do not define total orderings (for '
+                'example,\n'
+                '  the two sets "{1,2}" and "{2,3}" are not equal, nor subsets '
+                'of one\n'
+                '  another, nor supersets of one another).  Accordingly, sets '
+                'are not\n'
+                '  appropriate arguments for functions which depend on total '
+                'ordering\n'
+                '  (for example, "min()", "max()", and "sorted()" produce '
+                'undefined\n'
+                '  results given a list of sets as inputs).\n'
+                '\n'
+                '  Comparison of sets enforces reflexivity of its elements.\n'
+                '\n'
+                '* Most other built-in types have no comparison methods '
+                'implemented,\n'
+                '  so they inherit the default comparison behavior.\n'
+                '\n'
+                'User-defined classes that customize their comparison behavior '
+                'should\n'
+                'follow some consistency rules, if possible:\n'
+                '\n'
+                '* Equality comparison should be reflexive. In other words, '
+                'identical\n'
+                '  objects should compare equal:\n'
+                '\n'
+                '     "x is y" implies "x == y"\n'
+                '\n'
+                '* Comparison should be symmetric. In other words, the '
+                'following\n'
+                '  expressions should have the same result:\n'
+                '\n'
+                '     "x == y" and "y == x"\n'
+                '\n'
+                '     "x != y" and "y != x"\n'
+                '\n'
+                '     "x < y" and "y > x"\n'
+                '\n'
+                '     "x <= y" and "y >= x"\n'
+                '\n'
+                '* Comparison should be transitive. The following '
+                '(non-exhaustive)\n'
+                '  examples illustrate that:\n'
+                '\n'
+                '     "x > y and y > z" implies "x > z"\n'
+                '\n'
+                '     "x < y and y <= z" implies "x < z"\n'
+                '\n'
+                '* Inverse comparison should result in the boolean negation. '
+                'In other\n'
+                '  words, the following expressions should have the same '
+                'result:\n'
+                '\n'
+                '     "x == y" and "not x != y"\n'
+                '\n'
+                '     "x < y" and "not x >= y" (for total ordering)\n'
+                '\n'
+                '     "x > y" and "not x <= y" (for total ordering)\n'
+                '\n'
+                '  The last two expressions apply to totally ordered '
+                'collections (e.g.\n'
+                '  to sequences, but not to sets or mappings). See also the\n'
+                '  "total_ordering()" decorator.\n'
+                '\n'
+                '* The "hash()" result should be consistent with equality. '
+                'Objects\n'
+                '  that are equal should either have the same hash value, or '
+                'be marked\n'
+                '  as unhashable.\n'
+                '\n'
+                'Python does not enforce these consistency rules. In fact, '
+                'the\n'
+                'not-a-number values are an example for not following these '
+                'rules.\n'
+                '\n'
+                '\n'
+                'Membership test operations\n'
+                '==========================\n'
+                '\n'
+                'The operators "in" and "not in" test for membership.  "x in '
+                's"\n'
+                'evaluates to "True" if *x* is a member of *s*, and "False" '
+                'otherwise.\n'
+                '"x not in s" returns the negation of "x in s".  All built-in '
+                'sequences\n'
+                'and set types support this as well as dictionary, for which '
+                '"in" tests\n'
+                'whether the dictionary has a given key. For container types '
+                'such as\n'
+                'list, tuple, set, frozenset, dict, or collections.deque, the\n'
+                'expression "x in y" is equivalent to "any(x is e or x == e '
+                'for e in\n'
+                'y)".\n'
+                '\n'
+                'For the string and bytes types, "x in y" is "True" if and '
+                'only if *x*\n'
+                'is a substring of *y*.  An equivalent test is "y.find(x) != '
+                '-1".\n'
+                'Empty strings are always considered to be a substring of any '
+                'other\n'
+                'string, so """ in "abc"" will return "True".\n'
+                '\n'
+                'For user-defined classes which define the "__contains__()" '
+                'method, "x\n'
+                'in y" returns "True" if "y.__contains__(x)" returns a true '
+                'value, and\n'
+                '"False" otherwise.\n'
+                '\n'
+                'For user-defined classes which do not define "__contains__()" '
+                'but do\n'
+                'define "__iter__()", "x in y" is "True" if some value "z" '
+                'with "x ==\n'
+                'z" is produced while iterating over "y".  If an exception is '
+                'raised\n'
+                'during the iteration, it is as if "in" raised that '
+                'exception.\n'
+                '\n'
+                'Lastly, the old-style iteration protocol is tried: if a class '
+                'defines\n'
+                '"__getitem__()", "x in y" is "True" if and only if there is a '
+                'non-\n'
+                'negative integer index *i* such that "x == y[i]", and all '
+                'lower\n'
+                'integer indices do not raise "IndexError" exception.  (If any '
+                'other\n'
+                'exception is raised, it is as if "in" raised that '
+                'exception).\n'
+                '\n'
+                'The operator "not in" is defined to have the inverse true '
+                'value of\n'
+                '"in".\n'
+                '\n'
+                '\n'
+                'Identity comparisons\n'
+                '====================\n'
+                '\n'
+                'The operators "is" and "is not" test for object identity: "x '
+                'is y" is\n'
+                'true if and only if *x* and *y* are the same object.  Object '
+                'identity\n'
+                'is determined using the "id()" function.  "x is not y" yields '
+                'the\n'
+                'inverse truth value. [4]\n',
+ 'compound': 'Compound statements\n'
+             '*******************\n'
+             '\n'
+             'Compound statements contain (groups of) other statements; they '
+             'affect\n'
+             'or control the execution of those other statements in some way.  '
+             'In\n'
+             'general, compound statements span multiple lines, although in '
+             'simple\n'
+             'incarnations a whole compound statement may be contained in one '
+             'line.\n'
+             '\n'
+             'The "if", "while" and "for" statements implement traditional '
+             'control\n'
+             'flow constructs.  "try" specifies exception handlers and/or '
+             'cleanup\n'
+             'code for a group of statements, while the "with" statement '
+             'allows the\n'
+             'execution of initialization and finalization code around a block '
+             'of\n'
+             'code.  Function and class definitions are also syntactically '
+             'compound\n'
+             'statements.\n'
+             '\n'
+             'A compound statement consists of one or more ‘clauses.’  A '
+             'clause\n'
+             'consists of a header and a ‘suite.’  The clause headers of a\n'
+             'particular compound statement are all at the same indentation '
+             'level.\n'
+             'Each clause header begins with a uniquely identifying keyword '
+             'and ends\n'
+             'with a colon.  A suite is a group of statements controlled by a\n'
+             'clause.  A suite can be one or more semicolon-separated simple\n'
+             'statements on the same line as the header, following the '
+             'header’s\n'
+             'colon, or it can be one or more indented statements on '
+             'subsequent\n'
+             'lines.  Only the latter form of a suite can contain nested '
+             'compound\n'
+             'statements; the following is illegal, mostly because it wouldn’t '
+             'be\n'
+             'clear to which "if" clause a following "else" clause would '
+             'belong:\n'
+             '\n'
+             '   if test1: if test2: print(x)\n'
+             '\n'
+             'Also note that the semicolon binds tighter than the colon in '
+             'this\n'
+             'context, so that in the following example, either all or none of '
+             'the\n'
+             '"print()" calls are executed:\n'
+             '\n'
+             '   if x < y < z: print(x); print(y); print(z)\n'
+             '\n'
+             'Summarizing:\n'
+             '\n'
+             '   compound_stmt ::= if_stmt\n'
+             '                     | while_stmt\n'
+             '                     | for_stmt\n'
+             '                     | try_stmt\n'
+             '                     | with_stmt\n'
+             '                     | funcdef\n'
+             '                     | classdef\n'
+             '                     | async_with_stmt\n'
+             '                     | async_for_stmt\n'
+             '                     | async_funcdef\n'
+             '   suite         ::= stmt_list NEWLINE | NEWLINE INDENT '
+             'statement+ DEDENT\n'
+             '   statement     ::= stmt_list NEWLINE | compound_stmt\n'
+             '   stmt_list     ::= simple_stmt (";" simple_stmt)* [";"]\n'
+             '\n'
+             'Note that statements always end in a "NEWLINE" possibly followed '
+             'by a\n'
+             '"DEDENT".  Also note that optional continuation clauses always '
+             'begin\n'
+             'with a keyword that cannot start a statement, thus there are no\n'
+             'ambiguities (the ‘dangling "else"’ problem is solved in Python '
+             'by\n'
+             'requiring nested "if" statements to be indented).\n'
+             '\n'
+             'The formatting of the grammar rules in the following sections '
+             'places\n'
+             'each clause on a separate line for clarity.\n'
+             '\n'
+             '\n'
+             'The "if" statement\n'
+             '==================\n'
+             '\n'
+             'The "if" statement is used for conditional execution:\n'
+             '\n'
+             '   if_stmt ::= "if" expression ":" suite\n'
+             '               ("elif" expression ":" suite)*\n'
+             '               ["else" ":" suite]\n'
+             '\n'
+             'It selects exactly one of the suites by evaluating the '
+             'expressions one\n'
+             'by one until one is found to be true (see section Boolean '
+             'operations\n'
+             'for the definition of true and false); then that suite is '
+             'executed\n'
+             '(and no other part of the "if" statement is executed or '
+             'evaluated).\n'
+             'If all expressions are false, the suite of the "else" clause, '
+             'if\n'
+             'present, is executed.\n'
+             '\n'
+             '\n'
+             'The "while" statement\n'
+             '=====================\n'
+             '\n'
+             'The "while" statement is used for repeated execution as long as '
+             'an\n'
+             'expression is true:\n'
+             '\n'
+             '   while_stmt ::= "while" expression ":" suite\n'
+             '                  ["else" ":" suite]\n'
+             '\n'
+             'This repeatedly tests the expression and, if it is true, '
+             'executes the\n'
+             'first suite; if the expression is false (which may be the first '
+             'time\n'
+             'it is tested) the suite of the "else" clause, if present, is '
+             'executed\n'
+             'and the loop terminates.\n'
+             '\n'
+             'A "break" statement executed in the first suite terminates the '
+             'loop\n'
+             'without executing the "else" clause’s suite.  A "continue" '
+             'statement\n'
+             'executed in the first suite skips the rest of the suite and goes '
+             'back\n'
+             'to testing the expression.\n'
+             '\n'
+             '\n'
+             'The "for" statement\n'
+             '===================\n'
+             '\n'
+             'The "for" statement is used to iterate over the elements of a '
+             'sequence\n'
+             '(such as a string, tuple or list) or other iterable object:\n'
+             '\n'
+             '   for_stmt ::= "for" target_list "in" expression_list ":" '
+             'suite\n'
+             '                ["else" ":" suite]\n'
+             '\n'
+             'The expression list is evaluated once; it should yield an '
+             'iterable\n'
+             'object.  An iterator is created for the result of the\n'
+             '"expression_list".  The suite is then executed once for each '
+             'item\n'
+             'provided by the iterator, in the order returned by the '
+             'iterator.  Each\n'
+             'item in turn is assigned to the target list using the standard '
+             'rules\n'
+             'for assignments (see Assignment statements), and then the suite '
+             'is\n'
+             'executed.  When the items are exhausted (which is immediately '
+             'when the\n'
+             'sequence is empty or an iterator raises a "StopIteration" '
+             'exception),\n'
+             'the suite in the "else" clause, if present, is executed, and the '
+             'loop\n'
+             'terminates.\n'
+             '\n'
+             'A "break" statement executed in the first suite terminates the '
+             'loop\n'
+             'without executing the "else" clause’s suite.  A "continue" '
+             'statement\n'
+             'executed in the first suite skips the rest of the suite and '
+             'continues\n'
+             'with the next item, or with the "else" clause if there is no '
+             'next\n'
+             'item.\n'
+             '\n'
+             'The for-loop makes assignments to the variables(s) in the target '
+             'list.\n'
+             'This overwrites all previous assignments to those variables '
+             'including\n'
+             'those made in the suite of the for-loop:\n'
+             '\n'
+             '   for i in range(10):\n'
+             '       print(i)\n'
+             '       i = 5             # this will not affect the for-loop\n'
+             '                         # because i will be overwritten with '
+             'the next\n'
+             '                         # index in the range\n'
+             '\n'
+             'Names in the target list are not deleted when the loop is '
+             'finished,\n'
+             'but if the sequence is empty, they will not have been assigned '
+             'to at\n'
+             'all by the loop.  Hint: the built-in function "range()" returns '
+             'an\n'
+             'iterator of integers suitable to emulate the effect of Pascal’s '
+             '"for i\n'
+             ':= a to b do"; e.g., "list(range(3))" returns the list "[0, 1, '
+             '2]".\n'
+             '\n'
+             'Note: There is a subtlety when the sequence is being modified by '
+             'the\n'
+             '  loop (this can only occur for mutable sequences, e.g. lists).  '
+             'An\n'
+             '  internal counter is used to keep track of which item is used '
+             'next,\n'
+             '  and this is incremented on each iteration.  When this counter '
+             'has\n'
+             '  reached the length of the sequence the loop terminates.  This '
+             'means\n'
+             '  that if the suite deletes the current (or a previous) item '
+             'from the\n'
+             '  sequence, the next item will be skipped (since it gets the '
+             'index of\n'
+             '  the current item which has already been treated).  Likewise, '
+             'if the\n'
+             '  suite inserts an item in the sequence before the current item, '
+             'the\n'
+             '  current item will be treated again the next time through the '
+             'loop.\n'
+             '  This can lead to nasty bugs that can be avoided by making a\n'
+             '  temporary copy using a slice of the whole sequence, e.g.,\n'
+             '\n'
+             '     for x in a[:]:\n'
+             '         if x < 0: a.remove(x)\n'
+             '\n'
+             '\n'
+             'The "try" statement\n'
+             '===================\n'
+             '\n'
+             'The "try" statement specifies exception handlers and/or cleanup '
+             'code\n'
+             'for a group of statements:\n'
+             '\n'
+             '   try_stmt  ::= try1_stmt | try2_stmt\n'
+             '   try1_stmt ::= "try" ":" suite\n'
+             '                 ("except" [expression ["as" identifier]] ":" '
+             'suite)+\n'
+             '                 ["else" ":" suite]\n'
+             '                 ["finally" ":" suite]\n'
+             '   try2_stmt ::= "try" ":" suite\n'
+             '                 "finally" ":" suite\n'
+             '\n'
+             'The "except" clause(s) specify one or more exception handlers. '
+             'When no\n'
+             'exception occurs in the "try" clause, no exception handler is\n'
+             'executed. When an exception occurs in the "try" suite, a search '
+             'for an\n'
+             'exception handler is started.  This search inspects the except '
+             'clauses\n'
+             'in turn until one is found that matches the exception.  An '
+             'expression-\n'
+             'less except clause, if present, must be last; it matches any\n'
+             'exception.  For an except clause with an expression, that '
+             'expression\n'
+             'is evaluated, and the clause matches the exception if the '
+             'resulting\n'
+             'object is “compatible” with the exception.  An object is '
+             'compatible\n'
+             'with an exception if it is the class or a base class of the '
+             'exception\n'
+             'object or a tuple containing an item compatible with the '
+             'exception.\n'
+             '\n'
+             'If no except clause matches the exception, the search for an '
+             'exception\n'
+             'handler continues in the surrounding code and on the invocation '
+             'stack.\n'
+             '[1]\n'
+             '\n'
+             'If the evaluation of an expression in the header of an except '
+             'clause\n'
+             'raises an exception, the original search for a handler is '
+             'canceled and\n'
+             'a search starts for the new exception in the surrounding code '
+             'and on\n'
+             'the call stack (it is treated as if the entire "try" statement '
+             'raised\n'
+             'the exception).\n'
+             '\n'
+             'When a matching except clause is found, the exception is '
+             'assigned to\n'
+             'the target specified after the "as" keyword in that except '
+             'clause, if\n'
+             'present, and the except clause’s suite is executed.  All except\n'
+             'clauses must have an executable block.  When the end of this '
+             'block is\n'
+             'reached, execution continues normally after the entire try '
+             'statement.\n'
+             '(This means that if two nested handlers exist for the same '
+             'exception,\n'
+             'and the exception occurs in the try clause of the inner handler, '
+             'the\n'
+             'outer handler will not handle the exception.)\n'
+             '\n'
+             'When an exception has been assigned using "as target", it is '
+             'cleared\n'
+             'at the end of the except clause.  This is as if\n'
+             '\n'
+             '   except E as N:\n'
+             '       foo\n'
+             '\n'
+             'was translated to\n'
+             '\n'
+             '   except E as N:\n'
+             '       try:\n'
+             '           foo\n'
+             '       finally:\n'
+             '           del N\n'
+             '\n'
+             'This means the exception must be assigned to a different name to '
+             'be\n'
+             'able to refer to it after the except clause.  Exceptions are '
+             'cleared\n'
+             'because with the traceback attached to them, they form a '
+             'reference\n'
+             'cycle with the stack frame, keeping all locals in that frame '
+             'alive\n'
+             'until the next garbage collection occurs.\n'
+             '\n'
+             'Before an except clause’s suite is executed, details about the\n'
+             'exception are stored in the "sys" module and can be accessed '
+             'via\n'
+             '"sys.exc_info()". "sys.exc_info()" returns a 3-tuple consisting '
+             'of the\n'
+             'exception class, the exception instance and a traceback object '
+             '(see\n'
+             'section The standard type hierarchy) identifying the point in '
+             'the\n'
+             'program where the exception occurred.  "sys.exc_info()" values '
+             'are\n'
+             'restored to their previous values (before the call) when '
+             'returning\n'
+             'from a function that handled an exception.\n'
+             '\n'
+             'The optional "else" clause is executed if the control flow '
+             'leaves the\n'
+             '"try" suite, no exception was raised, and no "return", '
+             '"continue", or\n'
+             '"break" statement was executed.  Exceptions in the "else" clause '
+             'are\n'
+             'not handled by the preceding "except" clauses.\n'
+             '\n'
+             'If "finally" is present, it specifies a ‘cleanup’ handler.  The '
+             '"try"\n'
+             'clause is executed, including any "except" and "else" clauses.  '
+             'If an\n'
+             'exception occurs in any of the clauses and is not handled, the\n'
+             'exception is temporarily saved. The "finally" clause is '
+             'executed.  If\n'
+             'there is a saved exception it is re-raised at the end of the '
+             '"finally"\n'
+             'clause.  If the "finally" clause raises another exception, the '
+             'saved\n'
+             'exception is set as the context of the new exception. If the '
+             '"finally"\n'
+             'clause executes a "return" or "break" statement, the saved '
+             'exception\n'
+             'is discarded:\n'
+             '\n'
+             '   >>> def f():\n'
+             '   ...     try:\n'
+             '   ...         1/0\n'
+             '   ...     finally:\n'
+             '   ...         return 42\n'
+             '   ...\n'
+             '   >>> f()\n'
+             '   42\n'
+             '\n'
+             'The exception information is not available to the program '
+             'during\n'
+             'execution of the "finally" clause.\n'
+             '\n'
+             'When a "return", "break" or "continue" statement is executed in '
+             'the\n'
+             '"try" suite of a "try"…"finally" statement, the "finally" clause '
+             'is\n'
+             'also executed ‘on the way out.’ A "continue" statement is '
+             'illegal in\n'
+             'the "finally" clause. (The reason is a problem with the current\n'
+             'implementation — this restriction may be lifted in the future).\n'
+             '\n'
+             'The return value of a function is determined by the last '
+             '"return"\n'
+             'statement executed.  Since the "finally" clause always executes, '
+             'a\n'
+             '"return" statement executed in the "finally" clause will always '
+             'be the\n'
+             'last one executed:\n'
+             '\n'
+             '   >>> def foo():\n'
+             '   ...     try:\n'
+             "   ...         return 'try'\n"
+             '   ...     finally:\n'
+             "   ...         return 'finally'\n"
+             '   ...\n'
+             '   >>> foo()\n'
+             "   'finally'\n"
+             '\n'
+             'Additional information on exceptions can be found in section\n'
+             'Exceptions, and information on using the "raise" statement to '
+             'generate\n'
+             'exceptions may be found in section The raise statement.\n'
+             '\n'
+             '\n'
+             'The "with" statement\n'
+             '====================\n'
+             '\n'
+             'The "with" statement is used to wrap the execution of a block '
+             'with\n'
+             'methods defined by a context manager (see section With '
+             'Statement\n'
+             'Context Managers). This allows common "try"…"except"…"finally" '
+             'usage\n'
+             'patterns to be encapsulated for convenient reuse.\n'
+             '\n'
+             '   with_stmt ::= "with" with_item ("," with_item)* ":" suite\n'
+             '   with_item ::= expression ["as" target]\n'
+             '\n'
+             'The execution of the "with" statement with one “item” proceeds '
+             'as\n'
+             'follows:\n'
+             '\n'
+             '1. The context expression (the expression given in the '
+             '"with_item")\n'
+             '   is evaluated to obtain a context manager.\n'
+             '\n'
+             '2. The context manager’s "__exit__()" is loaded for later use.\n'
+             '\n'
+             '3. The context manager’s "__enter__()" method is invoked.\n'
+             '\n'
+             '4. If a target was included in the "with" statement, the return\n'
+             '   value from "__enter__()" is assigned to it.\n'
+             '\n'
+             '   Note: The "with" statement guarantees that if the '
+             '"__enter__()"\n'
+             '     method returns without an error, then "__exit__()" will '
+             'always be\n'
+             '     called. Thus, if an error occurs during the assignment to '
+             'the\n'
+             '     target list, it will be treated the same as an error '
+             'occurring\n'
+             '     within the suite would be. See step 6 below.\n'
+             '\n'
+             '5. The suite is executed.\n'
+             '\n'
+             '6. The context manager’s "__exit__()" method is invoked.  If an\n'
+             '   exception caused the suite to be exited, its type, value, '
+             'and\n'
+             '   traceback are passed as arguments to "__exit__()". Otherwise, '
+             'three\n'
+             '   "None" arguments are supplied.\n'
+             '\n'
+             '   If the suite was exited due to an exception, and the return '
+             'value\n'
+             '   from the "__exit__()" method was false, the exception is '
+             'reraised.\n'
+             '   If the return value was true, the exception is suppressed, '
+             'and\n'
+             '   execution continues with the statement following the "with"\n'
+             '   statement.\n'
+             '\n'
+             '   If the suite was exited for any reason other than an '
+             'exception, the\n'
+             '   return value from "__exit__()" is ignored, and execution '
+             'proceeds\n'
+             '   at the normal location for the kind of exit that was taken.\n'
+             '\n'
+             'With more than one item, the context managers are processed as '
+             'if\n'
+             'multiple "with" statements were nested:\n'
+             '\n'
+             '   with A() as a, B() as b:\n'
+             '       suite\n'
+             '\n'
+             'is equivalent to\n'
+             '\n'
+             '   with A() as a:\n'
+             '       with B() as b:\n'
+             '           suite\n'
+             '\n'
+             'Changed in version 3.1: Support for multiple context '
+             'expressions.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 343** - The “with” statement\n'
+             '     The specification, background, and examples for the Python '
+             '"with"\n'
+             '     statement.\n'
+             '\n'
+             '\n'
+             'Function definitions\n'
+             '====================\n'
+             '\n'
+             'A function definition defines a user-defined function object '
+             '(see\n'
+             'section The standard type hierarchy):\n'
+             '\n'
+             '   funcdef                 ::= [decorators] "def" funcname "(" '
+             '[parameter_list] ")"\n'
+             '               ["->" expression] ":" suite\n'
+             '   decorators              ::= decorator+\n'
+             '   decorator               ::= "@" dotted_name ["(" '
+             '[argument_list [","]] ")"] NEWLINE\n'
+             '   dotted_name             ::= identifier ("." identifier)*\n'
+             '   parameter_list          ::= defparameter ("," defparameter)* '
+             '["," [parameter_list_starargs]]\n'
+             '                      | parameter_list_starargs\n'
+             '   parameter_list_starargs ::= "*" [parameter] ("," '
+             'defparameter)* ["," ["**" parameter [","]]]\n'
+             '                               | "**" parameter [","]\n'
+             '   parameter               ::= identifier [":" expression]\n'
+             '   defparameter            ::= parameter ["=" expression]\n'
+             '   funcname                ::= identifier\n'
+             '\n'
+             'A function definition is an executable statement.  Its execution '
+             'binds\n'
+             'the function name in the current local namespace to a function '
+             'object\n'
+             '(a wrapper around the executable code for the function).  This\n'
+             'function object contains a reference to the current global '
+             'namespace\n'
+             'as the global namespace to be used when the function is called.\n'
+             '\n'
+             'The function definition does not execute the function body; this '
+             'gets\n'
+             'executed only when the function is called. [2]\n'
+             '\n'
+             'A function definition may be wrapped by one or more *decorator*\n'
+             'expressions. Decorator expressions are evaluated when the '
+             'function is\n'
+             'defined, in the scope that contains the function definition.  '
+             'The\n'
+             'result must be a callable, which is invoked with the function '
+             'object\n'
+             'as the only argument. The returned value is bound to the '
+             'function name\n'
+             'instead of the function object.  Multiple decorators are applied '
+             'in\n'
+             'nested fashion. For example, the following code\n'
+             '\n'
+             '   @f1(arg)\n'
+             '   @f2\n'
+             '   def func(): pass\n'
+             '\n'
+             'is roughly equivalent to\n'
+             '\n'
+             '   def func(): pass\n'
+             '   func = f1(arg)(f2(func))\n'
+             '\n'
+             'except that the original function is not temporarily bound to '
+             'the name\n'
+             '"func".\n'
+             '\n'
+             'When one or more *parameters* have the form *parameter* "="\n'
+             '*expression*, the function is said to have “default parameter '
+             'values.”\n'
+             'For a parameter with a default value, the corresponding '
+             '*argument* may\n'
+             'be omitted from a call, in which case the parameter’s default '
+             'value is\n'
+             'substituted.  If a parameter has a default value, all following\n'
+             'parameters up until the “"*"” must also have a default value — '
+             'this is\n'
+             'a syntactic restriction that is not expressed by the grammar.\n'
+             '\n'
+             '**Default parameter values are evaluated from left to right when '
+             'the\n'
+             'function definition is executed.** This means that the '
+             'expression is\n'
+             'evaluated once, when the function is defined, and that the same '
+             '“pre-\n'
+             'computed” value is used for each call.  This is especially '
+             'important\n'
+             'to understand when a default parameter is a mutable object, such '
+             'as a\n'
+             'list or a dictionary: if the function modifies the object (e.g. '
+             'by\n'
+             'appending an item to a list), the default value is in effect '
+             'modified.\n'
+             'This is generally not what was intended.  A way around this is '
+             'to use\n'
+             '"None" as the default, and explicitly test for it in the body of '
+             'the\n'
+             'function, e.g.:\n'
+             '\n'
+             '   def whats_on_the_telly(penguin=None):\n'
+             '       if penguin is None:\n'
+             '           penguin = []\n'
+             '       penguin.append("property of the zoo")\n'
+             '       return penguin\n'
+             '\n'
+             'Function call semantics are described in more detail in section '
+             'Calls.\n'
+             'A function call always assigns values to all parameters '
+             'mentioned in\n'
+             'the parameter list, either from position arguments, from '
+             'keyword\n'
+             'arguments, or from default values.  If the form “"*identifier"” '
+             'is\n'
+             'present, it is initialized to a tuple receiving any excess '
+             'positional\n'
+             'parameters, defaulting to the empty tuple. If the form\n'
+             '“"**identifier"” is present, it is initialized to a new ordered\n'
+             'mapping receiving any excess keyword arguments, defaulting to a '
+             'new\n'
+             'empty mapping of the same type.  Parameters after “"*"” or\n'
+             '“"*identifier"” are keyword-only parameters and may only be '
+             'passed\n'
+             'used keyword arguments.\n'
+             '\n'
+             'Parameters may have annotations of the form “": expression"” '
+             'following\n'
+             'the parameter name.  Any parameter may have an annotation even '
+             'those\n'
+             'of the form "*identifier" or "**identifier".  Functions may '
+             'have\n'
+             '“return” annotation of the form “"-> expression"” after the '
+             'parameter\n'
+             'list.  These annotations can be any valid Python expression and '
+             'are\n'
+             'evaluated when the function definition is executed.  Annotations '
+             'may\n'
+             'be evaluated in a different order than they appear in the source '
+             'code.\n'
+             'The presence of annotations does not change the semantics of a\n'
+             'function.  The annotation values are available as values of a\n'
+             'dictionary keyed by the parameters’ names in the '
+             '"__annotations__"\n'
+             'attribute of the function object.\n'
+             '\n'
+             'It is also possible to create anonymous functions (functions not '
+             'bound\n'
+             'to a name), for immediate use in expressions.  This uses lambda\n'
+             'expressions, described in section Lambdas.  Note that the '
+             'lambda\n'
+             'expression is merely a shorthand for a simplified function '
+             'definition;\n'
+             'a function defined in a “"def"” statement can be passed around '
+             'or\n'
+             'assigned to another name just like a function defined by a '
+             'lambda\n'
+             'expression.  The “"def"” form is actually more powerful since '
+             'it\n'
+             'allows the execution of multiple statements and annotations.\n'
+             '\n'
+             '**Programmer’s note:** Functions are first-class objects.  A '
+             '“"def"”\n'
+             'statement executed inside a function definition defines a local\n'
+             'function that can be returned or passed around.  Free variables '
+             'used\n'
+             'in the nested function can access the local variables of the '
+             'function\n'
+             'containing the def.  See section Naming and binding for '
+             'details.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 3107** - Function Annotations\n'
+             '     The original specification for function annotations.\n'
+             '\n'
+             '\n'
+             'Class definitions\n'
+             '=================\n'
+             '\n'
+             'A class definition defines a class object (see section The '
+             'standard\n'
+             'type hierarchy):\n'
+             '\n'
+             '   classdef    ::= [decorators] "class" classname [inheritance] '
+             '":" suite\n'
+             '   inheritance ::= "(" [argument_list] ")"\n'
+             '   classname   ::= identifier\n'
+             '\n'
+             'A class definition is an executable statement.  The inheritance '
+             'list\n'
+             'usually gives a list of base classes (see Metaclasses for more\n'
+             'advanced uses), so each item in the list should evaluate to a '
+             'class\n'
+             'object which allows subclassing.  Classes without an inheritance '
+             'list\n'
+             'inherit, by default, from the base class "object"; hence,\n'
+             '\n'
+             '   class Foo:\n'
+             '       pass\n'
+             '\n'
+             'is equivalent to\n'
+             '\n'
+             '   class Foo(object):\n'
+             '       pass\n'
+             '\n'
+             'The class’s suite is then executed in a new execution frame '
+             '(see\n'
+             'Naming and binding), using a newly created local namespace and '
+             'the\n'
+             'original global namespace. (Usually, the suite contains mostly\n'
+             'function definitions.)  When the class’s suite finishes '
+             'execution, its\n'
+             'execution frame is discarded but its local namespace is saved. '
+             '[3] A\n'
+             'class object is then created using the inheritance list for the '
+             'base\n'
+             'classes and the saved local namespace for the attribute '
+             'dictionary.\n'
+             'The class name is bound to this class object in the original '
+             'local\n'
+             'namespace.\n'
+             '\n'
+             'The order in which attributes are defined in the class body is\n'
+             'preserved in the new class’s "__dict__".  Note that this is '
+             'reliable\n'
+             'only right after the class is created and only for classes that '
+             'were\n'
+             'defined using the definition syntax.\n'
+             '\n'
+             'Class creation can be customized heavily using metaclasses.\n'
+             '\n'
+             'Classes can also be decorated: just like when decorating '
+             'functions,\n'
+             '\n'
+             '   @f1(arg)\n'
+             '   @f2\n'
+             '   class Foo: pass\n'
+             '\n'
+             'is roughly equivalent to\n'
+             '\n'
+             '   class Foo: pass\n'
+             '   Foo = f1(arg)(f2(Foo))\n'
+             '\n'
+             'The evaluation rules for the decorator expressions are the same '
+             'as for\n'
+             'function decorators.  The result is then bound to the class '
+             'name.\n'
+             '\n'
+             '**Programmer’s note:** Variables defined in the class definition '
+             'are\n'
+             'class attributes; they are shared by instances.  Instance '
+             'attributes\n'
+             'can be set in a method with "self.name = value".  Both class '
+             'and\n'
+             'instance attributes are accessible through the notation '
+             '“"self.name"”,\n'
+             'and an instance attribute hides a class attribute with the same '
+             'name\n'
+             'when accessed in this way.  Class attributes can be used as '
+             'defaults\n'
+             'for instance attributes, but using mutable values there can lead '
+             'to\n'
+             'unexpected results.  Descriptors can be used to create instance\n'
+             'variables with different implementation details.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 3115** - Metaclasses in Python 3000\n'
+             '     The proposal that changed the declaration of metaclasses to '
+             'the\n'
+             '     current syntax, and the semantics for how classes with\n'
+             '     metaclasses are constructed.\n'
+             '\n'
+             '  **PEP 3129** - Class Decorators\n'
+             '     The proposal that added class decorators.  Function and '
+             'method\n'
+             '     decorators were introduced in **PEP 318**.\n'
+             '\n'
+             '\n'
+             'Coroutines\n'
+             '==========\n'
+             '\n'
+             'New in version 3.5.\n'
+             '\n'
+             '\n'
+             'Coroutine function definition\n'
+             '-----------------------------\n'
+             '\n'
+             '   async_funcdef ::= [decorators] "async" "def" funcname "(" '
+             '[parameter_list] ")"\n'
+             '                     ["->" expression] ":" suite\n'
+             '\n'
+             'Execution of Python coroutines can be suspended and resumed at '
+             'many\n'
+             'points (see *coroutine*).  In the body of a coroutine, any '
+             '"await" and\n'
+             '"async" identifiers become reserved keywords; "await" '
+             'expressions,\n'
+             '"async for" and "async with" can only be used in coroutine '
+             'bodies.\n'
+             '\n'
+             'Functions defined with "async def" syntax are always coroutine\n'
+             'functions, even if they do not contain "await" or "async" '
+             'keywords.\n'
+             '\n'
+             'It is a "SyntaxError" to use "yield from" expressions in "async '
+             'def"\n'
+             'coroutines.\n'
+             '\n'
+             'An example of a coroutine function:\n'
+             '\n'
+             '   async def func(param1, param2):\n'
+             '       do_stuff()\n'
+             '       await some_coroutine()\n'
+             '\n'
+             '\n'
+             'The "async for" statement\n'
+             '-------------------------\n'
+             '\n'
+             '   async_for_stmt ::= "async" for_stmt\n'
+             '\n'
+             'An *asynchronous iterable* is able to call asynchronous code in '
+             'its\n'
+             '*iter* implementation, and *asynchronous iterator* can call\n'
+             'asynchronous code in its *next* method.\n'
+             '\n'
+             'The "async for" statement allows convenient iteration over\n'
+             'asynchronous iterators.\n'
+             '\n'
+             'The following code:\n'
+             '\n'
+             '   async for TARGET in ITER:\n'
+             '       BLOCK\n'
+             '   else:\n'
+             '       BLOCK2\n'
+             '\n'
+             'Is semantically equivalent to:\n'
+             '\n'
+             '   iter = (ITER)\n'
+             '   iter = type(iter).__aiter__(iter)\n'
+             '   running = True\n'
+             '   while running:\n'
+             '       try:\n'
+             '           TARGET = await type(iter).__anext__(iter)\n'
+             '       except StopAsyncIteration:\n'
+             '           running = False\n'
+             '       else:\n'
+             '           BLOCK\n'
+             '   else:\n'
+             '       BLOCK2\n'
+             '\n'
+             'See also "__aiter__()" and "__anext__()" for details.\n'
+             '\n'
+             'It is a "SyntaxError" to use "async for" statement outside of '
+             'an\n'
+             '"async def" function.\n'
+             '\n'
+             '\n'
+             'The "async with" statement\n'
+             '--------------------------\n'
+             '\n'
+             '   async_with_stmt ::= "async" with_stmt\n'
+             '\n'
+             'An *asynchronous context manager* is a *context manager* that is '
+             'able\n'
+             'to suspend execution in its *enter* and *exit* methods.\n'
+             '\n'
+             'The following code:\n'
+             '\n'
+             '   async with EXPR as VAR:\n'
+             '       BLOCK\n'
+             '\n'
+             'Is semantically equivalent to:\n'
+             '\n'
+             '   mgr = (EXPR)\n'
+             '   aexit = type(mgr).__aexit__\n'
+             '   aenter = type(mgr).__aenter__(mgr)\n'
+             '\n'
+             '   VAR = await aenter\n'
+             '   try:\n'
+             '       BLOCK\n'
+             '   except:\n'
+             '       if not await aexit(mgr, *sys.exc_info()):\n'
+             '           raise\n'
+             '   else:\n'
+             '       await aexit(mgr, None, None, None)\n'
+             '\n'
+             'See also "__aenter__()" and "__aexit__()" for details.\n'
+             '\n'
+             'It is a "SyntaxError" to use "async with" statement outside of '
+             'an\n'
+             '"async def" function.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 492** - Coroutines with async and await syntax\n'
+             '     The proposal that made coroutines a proper standalone '
+             'concept in\n'
+             '     Python, and added supporting syntax.\n'
+             '\n'
+             '-[ Footnotes ]-\n'
+             '\n'
+             '[1] The exception is propagated to the invocation stack unless\n'
+             '    there is a "finally" clause which happens to raise another\n'
+             '    exception. That new exception causes the old one to be '
+             'lost.\n'
+             '\n'
+             '[2] A string literal appearing as the first statement in the\n'
+             '    function body is transformed into the function’s "__doc__"\n'
+             '    attribute and therefore the function’s *docstring*.\n'
+             '\n'
+             '[3] A string literal appearing as the first statement in the '
+             'class\n'
+             '    body is transformed into the namespace’s "__doc__" item and\n'
+             '    therefore the class’s *docstring*.\n',
+ 'context-managers': 'With Statement Context Managers\n'
+                     '*******************************\n'
+                     '\n'
+                     'A *context manager* is an object that defines the '
+                     'runtime context to\n'
+                     'be established when executing a "with" statement. The '
+                     'context manager\n'
+                     'handles the entry into, and the exit from, the desired '
+                     'runtime context\n'
+                     'for the execution of the block of code.  Context '
+                     'managers are normally\n'
+                     'invoked using the "with" statement (described in section '
+                     'The with\n'
+                     'statement), but can also be used by directly invoking '
+                     'their methods.\n'
+                     '\n'
+                     'Typical uses of context managers include saving and '
+                     'restoring various\n'
+                     'kinds of global state, locking and unlocking resources, '
+                     'closing opened\n'
+                     'files, etc.\n'
+                     '\n'
+                     'For more information on context managers, see Context '
+                     'Manager Types.\n'
+                     '\n'
+                     'object.__enter__(self)\n'
+                     '\n'
+                     '   Enter the runtime context related to this object. The '
+                     '"with"\n'
+                     '   statement will bind this method’s return value to the '
+                     'target(s)\n'
+                     '   specified in the "as" clause of the statement, if '
+                     'any.\n'
+                     '\n'
+                     'object.__exit__(self, exc_type, exc_value, traceback)\n'
+                     '\n'
+                     '   Exit the runtime context related to this object. The '
+                     'parameters\n'
+                     '   describe the exception that caused the context to be '
+                     'exited. If the\n'
+                     '   context was exited without an exception, all three '
+                     'arguments will\n'
+                     '   be "None".\n'
+                     '\n'
+                     '   If an exception is supplied, and the method wishes to '
+                     'suppress the\n'
+                     '   exception (i.e., prevent it from being propagated), '
+                     'it should\n'
+                     '   return a true value. Otherwise, the exception will be '
+                     'processed\n'
+                     '   normally upon exit from this method.\n'
+                     '\n'
+                     '   Note that "__exit__()" methods should not reraise the '
+                     'passed-in\n'
+                     '   exception; this is the caller’s responsibility.\n'
+                     '\n'
+                     'See also:\n'
+                     '\n'
+                     '  **PEP 343** - The “with” statement\n'
+                     '     The specification, background, and examples for the '
+                     'Python "with"\n'
+                     '     statement.\n',
+ 'continue': 'The "continue" statement\n'
+             '************************\n'
+             '\n'
+             '   continue_stmt ::= "continue"\n'
+             '\n'
+             '"continue" may only occur syntactically nested in a "for" or '
+             '"while"\n'
+             'loop, but not nested in a function or class definition or '
+             '"finally"\n'
+             'clause within that loop.  It continues with the next cycle of '
+             'the\n'
+             'nearest enclosing loop.\n'
+             '\n'
+             'When "continue" passes control out of a "try" statement with a\n'
+             '"finally" clause, that "finally" clause is executed before '
+             'really\n'
+             'starting the next loop cycle.\n',
+ 'conversions': 'Arithmetic conversions\n'
+                '**********************\n'
+                '\n'
+                'When a description of an arithmetic operator below uses the '
+                'phrase\n'
+                '“the numeric arguments are converted to a common type,” this '
+                'means\n'
+                'that the operator implementation for built-in types works as '
+                'follows:\n'
+                '\n'
+                '* If either argument is a complex number, the other is '
+                'converted to\n'
+                '  complex;\n'
+                '\n'
+                '* otherwise, if either argument is a floating point number, '
+                'the\n'
+                '  other is converted to floating point;\n'
+                '\n'
+                '* otherwise, both must be integers and no conversion is '
+                'necessary.\n'
+                '\n'
+                'Some additional rules apply for certain operators (e.g., a '
+                'string as a\n'
+                'left argument to the ‘%’ operator).  Extensions must define '
+                'their own\n'
+                'conversion behavior.\n',
+ 'customization': 'Basic customization\n'
+                  '*******************\n'
+                  '\n'
+                  'object.__new__(cls[, ...])\n'
+                  '\n'
+                  '   Called to create a new instance of class *cls*.  '
+                  '"__new__()" is a\n'
+                  '   static method (special-cased so you need not declare it '
+                  'as such)\n'
+                  '   that takes the class of which an instance was requested '
+                  'as its\n'
+                  '   first argument.  The remaining arguments are those '
+                  'passed to the\n'
+                  '   object constructor expression (the call to the class).  '
+                  'The return\n'
+                  '   value of "__new__()" should be the new object instance '
+                  '(usually an\n'
+                  '   instance of *cls*).\n'
+                  '\n'
+                  '   Typical implementations create a new instance of the '
+                  'class by\n'
+                  '   invoking the superclass’s "__new__()" method using\n'
+                  '   "super().__new__(cls[, ...])" with appropriate arguments '
+                  'and then\n'
+                  '   modifying the newly-created instance as necessary before '
+                  'returning\n'
+                  '   it.\n'
+                  '\n'
+                  '   If "__new__()" returns an instance of *cls*, then the '
+                  'new\n'
+                  '   instance’s "__init__()" method will be invoked like\n'
+                  '   "__init__(self[, ...])", where *self* is the new '
+                  'instance and the\n'
+                  '   remaining arguments are the same as were passed to '
+                  '"__new__()".\n'
+                  '\n'
+                  '   If "__new__()" does not return an instance of *cls*, '
+                  'then the new\n'
+                  '   instance’s "__init__()" method will not be invoked.\n'
+                  '\n'
+                  '   "__new__()" is intended mainly to allow subclasses of '
+                  'immutable\n'
+                  '   types (like int, str, or tuple) to customize instance '
+                  'creation.  It\n'
+                  '   is also commonly overridden in custom metaclasses in '
+                  'order to\n'
+                  '   customize class creation.\n'
+                  '\n'
+                  'object.__init__(self[, ...])\n'
+                  '\n'
+                  '   Called after the instance has been created (by '
+                  '"__new__()"), but\n'
+                  '   before it is returned to the caller.  The arguments are '
+                  'those\n'
+                  '   passed to the class constructor expression.  If a base '
+                  'class has an\n'
+                  '   "__init__()" method, the derived class’s "__init__()" '
+                  'method, if\n'
+                  '   any, must explicitly call it to ensure proper '
+                  'initialization of the\n'
+                  '   base class part of the instance; for example:\n'
+                  '   "super().__init__([args...])".\n'
+                  '\n'
+                  '   Because "__new__()" and "__init__()" work together in '
+                  'constructing\n'
+                  '   objects ("__new__()" to create it, and "__init__()" to '
+                  'customize\n'
+                  '   it), no non-"None" value may be returned by '
+                  '"__init__()"; doing so\n'
+                  '   will cause a "TypeError" to be raised at runtime.\n'
+                  '\n'
+                  'object.__del__(self)\n'
+                  '\n'
+                  '   Called when the instance is about to be destroyed.  This '
+                  'is also\n'
+                  '   called a finalizer or (improperly) a destructor.  If a '
+                  'base class\n'
+                  '   has a "__del__()" method, the derived class’s '
+                  '"__del__()" method,\n'
+                  '   if any, must explicitly call it to ensure proper '
+                  'deletion of the\n'
+                  '   base class part of the instance.\n'
+                  '\n'
+                  '   It is possible (though not recommended!) for the '
+                  '"__del__()" method\n'
+                  '   to postpone destruction of the instance by creating a '
+                  'new reference\n'
+                  '   to it.  This is called object *resurrection*.  It is\n'
+                  '   implementation-dependent whether "__del__()" is called a '
+                  'second\n'
+                  '   time when a resurrected object is about to be destroyed; '
+                  'the\n'
+                  '   current *CPython* implementation only calls it once.\n'
+                  '\n'
+                  '   It is not guaranteed that "__del__()" methods are called '
+                  'for\n'
+                  '   objects that still exist when the interpreter exits.\n'
+                  '\n'
+                  '   Note: "del x" doesn’t directly call "x.__del__()" — the '
+                  'former\n'
+                  '     decrements the reference count for "x" by one, and the '
+                  'latter is\n'
+                  '     only called when "x"’s reference count reaches zero.\n'
+                  '\n'
+                  '   **CPython implementation detail:** It is possible for a '
+                  'reference\n'
+                  '   cycle to prevent the reference count of an object from '
+                  'going to\n'
+                  '   zero.  In this case, the cycle will be later detected '
+                  'and deleted\n'
+                  '   by the *cyclic garbage collector*.  A common cause of '
+                  'reference\n'
+                  '   cycles is when an exception has been caught in a local '
+                  'variable.\n'
+                  '   The frame’s locals then reference the exception, which '
+                  'references\n'
+                  '   its own traceback, which references the locals of all '
+                  'frames caught\n'
+                  '   in the traceback.\n'
+                  '\n'
+                  '   See also: Documentation for the "gc" module.\n'
+                  '\n'
+                  '   Warning: Due to the precarious circumstances under '
+                  'which\n'
+                  '     "__del__()" methods are invoked, exceptions that occur '
+                  'during\n'
+                  '     their execution are ignored, and a warning is printed '
+                  'to\n'
+                  '     "sys.stderr" instead. In particular:\n'
+                  '\n'
+                  '     * "__del__()" can be invoked when arbitrary code is '
+                  'being\n'
+                  '       executed, including from any arbitrary thread.  If '
+                  '"__del__()"\n'
+                  '       needs to take a lock or invoke any other blocking '
+                  'resource, it\n'
+                  '       may deadlock as the resource may already be taken by '
+                  'the code\n'
+                  '       that gets interrupted to execute "__del__()".\n'
+                  '\n'
+                  '     * "__del__()" can be executed during interpreter '
+                  'shutdown.  As\n'
+                  '       a consequence, the global variables it needs to '
+                  'access\n'
+                  '       (including other modules) may already have been '
+                  'deleted or set\n'
+                  '       to "None". Python guarantees that globals whose name '
+                  'begins\n'
+                  '       with a single underscore are deleted from their '
+                  'module before\n'
+                  '       other globals are deleted; if no other references to '
+                  'such\n'
+                  '       globals exist, this may help in assuring that '
+                  'imported modules\n'
+                  '       are still available at the time when the "__del__()" '
+                  'method is\n'
+                  '       called.\n'
+                  '\n'
+                  'object.__repr__(self)\n'
+                  '\n'
+                  '   Called by the "repr()" built-in function to compute the '
+                  '“official”\n'
+                  '   string representation of an object.  If at all possible, '
+                  'this\n'
+                  '   should look like a valid Python expression that could be '
+                  'used to\n'
+                  '   recreate an object with the same value (given an '
+                  'appropriate\n'
+                  '   environment).  If this is not possible, a string of the '
+                  'form\n'
+                  '   "<...some useful description...>" should be returned. '
+                  'The return\n'
+                  '   value must be a string object. If a class defines '
+                  '"__repr__()" but\n'
+                  '   not "__str__()", then "__repr__()" is also used when an '
+                  '“informal”\n'
+                  '   string representation of instances of that class is '
+                  'required.\n'
+                  '\n'
+                  '   This is typically used for debugging, so it is important '
+                  'that the\n'
+                  '   representation is information-rich and unambiguous.\n'
+                  '\n'
+                  'object.__str__(self)\n'
+                  '\n'
+                  '   Called by "str(object)" and the built-in functions '
+                  '"format()" and\n'
+                  '   "print()" to compute the “informal” or nicely printable '
+                  'string\n'
+                  '   representation of an object.  The return value must be a '
+                  'string\n'
+                  '   object.\n'
+                  '\n'
+                  '   This method differs from "object.__repr__()" in that '
+                  'there is no\n'
+                  '   expectation that "__str__()" return a valid Python '
+                  'expression: a\n'
+                  '   more convenient or concise representation can be used.\n'
+                  '\n'
+                  '   The default implementation defined by the built-in type '
+                  '"object"\n'
+                  '   calls "object.__repr__()".\n'
+                  '\n'
+                  'object.__bytes__(self)\n'
+                  '\n'
+                  '   Called by bytes to compute a byte-string representation '
+                  'of an\n'
+                  '   object. This should return a "bytes" object.\n'
+                  '\n'
+                  'object.__format__(self, format_spec)\n'
+                  '\n'
+                  '   Called by the "format()" built-in function, and by '
+                  'extension,\n'
+                  '   evaluation of formatted string literals and the '
+                  '"str.format()"\n'
+                  '   method, to produce a “formatted” string representation '
+                  'of an\n'
+                  '   object. The "format_spec" argument is a string that '
+                  'contains a\n'
+                  '   description of the formatting options desired. The '
+                  'interpretation\n'
+                  '   of the "format_spec" argument is up to the type '
+                  'implementing\n'
+                  '   "__format__()", however most classes will either '
+                  'delegate\n'
+                  '   formatting to one of the built-in types, or use a '
+                  'similar\n'
+                  '   formatting option syntax.\n'
+                  '\n'
+                  '   See Format Specification Mini-Language for a description '
+                  'of the\n'
+                  '   standard formatting syntax.\n'
+                  '\n'
+                  '   The return value must be a string object.\n'
+                  '\n'
+                  '   Changed in version 3.4: The __format__ method of '
+                  '"object" itself\n'
+                  '   raises a "TypeError" if passed any non-empty string.\n'
+                  '\n'
+                  'object.__lt__(self, other)\n'
+                  'object.__le__(self, other)\n'
+                  'object.__eq__(self, other)\n'
+                  'object.__ne__(self, other)\n'
+                  'object.__gt__(self, other)\n'
+                  'object.__ge__(self, other)\n'
+                  '\n'
+                  '   These are the so-called “rich comparison” methods. The\n'
+                  '   correspondence between operator symbols and method names '
+                  'is as\n'
+                  '   follows: "x<y" calls "x.__lt__(y)", "x<=y" calls '
+                  '"x.__le__(y)",\n'
+                  '   "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", '
+                  '"x>y" calls\n'
+                  '   "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n'
+                  '\n'
+                  '   A rich comparison method may return the singleton '
+                  '"NotImplemented"\n'
+                  '   if it does not implement the operation for a given pair '
+                  'of\n'
+                  '   arguments. By convention, "False" and "True" are '
+                  'returned for a\n'
+                  '   successful comparison. However, these methods can return '
+                  'any value,\n'
+                  '   so if the comparison operator is used in a Boolean '
+                  'context (e.g.,\n'
+                  '   in the condition of an "if" statement), Python will call '
+                  '"bool()"\n'
+                  '   on the value to determine if the result is true or '
+                  'false.\n'
+                  '\n'
+                  '   By default, "__ne__()" delegates to "__eq__()" and '
+                  'inverts the\n'
+                  '   result unless it is "NotImplemented".  There are no '
+                  'other implied\n'
+                  '   relationships among the comparison operators, for '
+                  'example, the\n'
+                  '   truth of "(x<y or x==y)" does not imply "x<=y". To '
+                  'automatically\n'
+                  '   generate ordering operations from a single root '
+                  'operation, see\n'
+                  '   "functools.total_ordering()".\n'
+                  '\n'
+                  '   See the paragraph on "__hash__()" for some important '
+                  'notes on\n'
+                  '   creating *hashable* objects which support custom '
+                  'comparison\n'
+                  '   operations and are usable as dictionary keys.\n'
+                  '\n'
+                  '   There are no swapped-argument versions of these methods '
+                  '(to be used\n'
+                  '   when the left argument does not support the operation '
+                  'but the right\n'
+                  '   argument does); rather, "__lt__()" and "__gt__()" are '
+                  'each other’s\n'
+                  '   reflection, "__le__()" and "__ge__()" are each other’s '
+                  'reflection,\n'
+                  '   and "__eq__()" and "__ne__()" are their own reflection. '
+                  'If the\n'
+                  '   operands are of different types, and right operand’s '
+                  'type is a\n'
+                  '   direct or indirect subclass of the left operand’s type, '
+                  'the\n'
+                  '   reflected method of the right operand has priority, '
+                  'otherwise the\n'
+                  '   left operand’s method has priority.  Virtual subclassing '
+                  'is not\n'
+                  '   considered.\n'
+                  '\n'
+                  'object.__hash__(self)\n'
+                  '\n'
+                  '   Called by built-in function "hash()" and for operations '
+                  'on members\n'
+                  '   of hashed collections including "set", "frozenset", and '
+                  '"dict".\n'
+                  '   "__hash__()" should return an integer. The only required '
+                  'property\n'
+                  '   is that objects which compare equal have the same hash '
+                  'value; it is\n'
+                  '   advised to mix together the hash values of the '
+                  'components of the\n'
+                  '   object that also play a part in comparison of objects by '
+                  'packing\n'
+                  '   them into a tuple and hashing the tuple. Example:\n'
+                  '\n'
+                  '      def __hash__(self):\n'
+                  '          return hash((self.name, self.nick, self.color))\n'
+                  '\n'
+                  '   Note: "hash()" truncates the value returned from an '
+                  'object’s\n'
+                  '     custom "__hash__()" method to the size of a '
+                  '"Py_ssize_t".  This\n'
+                  '     is typically 8 bytes on 64-bit builds and 4 bytes on '
+                  '32-bit\n'
+                  '     builds. If an object’s   "__hash__()" must '
+                  'interoperate on builds\n'
+                  '     of different bit sizes, be sure to check the width on '
+                  'all\n'
+                  '     supported builds.  An easy way to do this is with '
+                  '"python -c\n'
+                  '     "import sys; print(sys.hash_info.width)"".\n'
+                  '\n'
+                  '   If a class does not define an "__eq__()" method it '
+                  'should not\n'
+                  '   define a "__hash__()" operation either; if it defines '
+                  '"__eq__()"\n'
+                  '   but not "__hash__()", its instances will not be usable '
+                  'as items in\n'
+                  '   hashable collections.  If a class defines mutable '
+                  'objects and\n'
+                  '   implements an "__eq__()" method, it should not '
+                  'implement\n'
+                  '   "__hash__()", since the implementation of hashable '
+                  'collections\n'
+                  '   requires that a key’s hash value is immutable (if the '
+                  'object’s hash\n'
+                  '   value changes, it will be in the wrong hash bucket).\n'
+                  '\n'
+                  '   User-defined classes have "__eq__()" and "__hash__()" '
+                  'methods by\n'
+                  '   default; with them, all objects compare unequal (except '
+                  'with\n'
+                  '   themselves) and "x.__hash__()" returns an appropriate '
+                  'value such\n'
+                  '   that "x == y" implies both that "x is y" and "hash(x) == '
+                  'hash(y)".\n'
+                  '\n'
+                  '   A class that overrides "__eq__()" and does not define '
+                  '"__hash__()"\n'
+                  '   will have its "__hash__()" implicitly set to "None".  '
+                  'When the\n'
+                  '   "__hash__()" method of a class is "None", instances of '
+                  'the class\n'
+                  '   will raise an appropriate "TypeError" when a program '
+                  'attempts to\n'
+                  '   retrieve their hash value, and will also be correctly '
+                  'identified as\n'
+                  '   unhashable when checking "isinstance(obj, '
+                  'collections.Hashable)".\n'
+                  '\n'
+                  '   If a class that overrides "__eq__()" needs to retain '
+                  'the\n'
+                  '   implementation of "__hash__()" from a parent class, the '
+                  'interpreter\n'
+                  '   must be told this explicitly by setting "__hash__ =\n'
+                  '   <ParentClass>.__hash__".\n'
+                  '\n'
+                  '   If a class that does not override "__eq__()" wishes to '
+                  'suppress\n'
+                  '   hash support, it should include "__hash__ = None" in the '
+                  'class\n'
+                  '   definition. A class which defines its own "__hash__()" '
+                  'that\n'
+                  '   explicitly raises a "TypeError" would be incorrectly '
+                  'identified as\n'
+                  '   hashable by an "isinstance(obj, collections.Hashable)" '
+                  'call.\n'
+                  '\n'
+                  '   Note: By default, the "__hash__()" values of str, bytes '
+                  'and\n'
+                  '     datetime objects are “salted” with an unpredictable '
+                  'random value.\n'
+                  '     Although they remain constant within an individual '
+                  'Python\n'
+                  '     process, they are not predictable between repeated '
+                  'invocations of\n'
+                  '     Python.This is intended to provide protection against '
+                  'a denial-\n'
+                  '     of-service caused by carefully-chosen inputs that '
+                  'exploit the\n'
+                  '     worst case performance of a dict insertion, O(n^2) '
+                  'complexity.\n'
+                  '     See '
+                  'http://www.ocert.org/advisories/ocert-2011-003.html for\n'
+                  '     details.Changing hash values affects the iteration '
+                  'order of\n'
+                  '     dicts, sets and other mappings.  Python has never made '
+                  'guarantees\n'
+                  '     about this ordering (and it typically varies between '
+                  '32-bit and\n'
+                  '     64-bit builds).See also "PYTHONHASHSEED".\n'
+                  '\n'
+                  '   Changed in version 3.3: Hash randomization is enabled by '
+                  'default.\n'
+                  '\n'
+                  'object.__bool__(self)\n'
+                  '\n'
+                  '   Called to implement truth value testing and the built-in '
+                  'operation\n'
+                  '   "bool()"; should return "False" or "True".  When this '
+                  'method is not\n'
+                  '   defined, "__len__()" is called, if it is defined, and '
+                  'the object is\n'
+                  '   considered true if its result is nonzero.  If a class '
+                  'defines\n'
+                  '   neither "__len__()" nor "__bool__()", all its instances '
+                  'are\n'
+                  '   considered true.\n',
+ 'debugger': '"pdb" — The Python Debugger\n'
+             '***************************\n'
+             '\n'
+             '**Source code:** Lib/pdb.py\n'
+             '\n'
+             '======================================================================\n'
+             '\n'
+             'The module "pdb" defines an interactive source code debugger '
+             'for\n'
+             'Python programs.  It supports setting (conditional) breakpoints '
+             'and\n'
+             'single stepping at the source line level, inspection of stack '
+             'frames,\n'
+             'source code listing, and evaluation of arbitrary Python code in '
+             'the\n'
+             'context of any stack frame.  It also supports post-mortem '
+             'debugging\n'
+             'and can be called under program control.\n'
+             '\n'
+             'The debugger is extensible – it is actually defined as the '
+             'class\n'
+             '"Pdb". This is currently undocumented but easily understood by '
+             'reading\n'
+             'the source.  The extension interface uses the modules "bdb" and '
+             '"cmd".\n'
+             '\n'
+             'The debugger’s prompt is "(Pdb)". Typical usage to run a program '
+             'under\n'
+             'control of the debugger is:\n'
+             '\n'
+             '   >>> import pdb\n'
+             '   >>> import mymodule\n'
+             "   >>> pdb.run('mymodule.test()')\n"
+             '   > <string>(0)?()\n'
+             '   (Pdb) continue\n'
+             '   > <string>(1)?()\n'
+             '   (Pdb) continue\n'
+             "   NameError: 'spam'\n"
+             '   > <string>(1)?()\n'
+             '   (Pdb)\n'
+             '\n'
+             'Changed in version 3.3: Tab-completion via the "readline" module '
+             'is\n'
+             'available for commands and command arguments, e.g. the current '
+             'global\n'
+             'and local names are offered as arguments of the "p" command.\n'
+             '\n'
+             '"pdb.py" can also be invoked as a script to debug other '
+             'scripts.  For\n'
+             'example:\n'
+             '\n'
+             '   python3 -m pdb myscript.py\n'
+             '\n'
+             'When invoked as a script, pdb will automatically enter '
+             'post-mortem\n'
+             'debugging if the program being debugged exits abnormally.  After '
+             'post-\n'
+             'mortem debugging (or after normal exit of the program), pdb '
+             'will\n'
+             'restart the program.  Automatic restarting preserves pdb’s state '
+             '(such\n'
+             'as breakpoints) and in most cases is more useful than quitting '
+             'the\n'
+             'debugger upon program’s exit.\n'
+             '\n'
+             'New in version 3.2: "pdb.py" now accepts a "-c" option that '
+             'executes\n'
+             'commands as if given in a ".pdbrc" file, see Debugger Commands.\n'
+             '\n'
+             'The typical usage to break into the debugger from a running '
+             'program is\n'
+             'to insert\n'
+             '\n'
+             '   import pdb; pdb.set_trace()\n'
+             '\n'
+             'at the location you want to break into the debugger.  You can '
+             'then\n'
+             'step through the code following this statement, and continue '
+             'running\n'
+             'without the debugger using the "continue" command.\n'
+             '\n'
+             'The typical usage to inspect a crashed program is:\n'
+             '\n'
+             '   >>> import pdb\n'
+             '   >>> import mymodule\n'
+             '   >>> mymodule.test()\n'
+             '   Traceback (most recent call last):\n'
+             '     File "<stdin>", line 1, in <module>\n'
+             '     File "./mymodule.py", line 4, in test\n'
+             '       test2()\n'
+             '     File "./mymodule.py", line 3, in test2\n'
+             '       print(spam)\n'
+             '   NameError: spam\n'
+             '   >>> pdb.pm()\n'
+             '   > ./mymodule.py(3)test2()\n'
+             '   -> print(spam)\n'
+             '   (Pdb)\n'
+             '\n'
+             'The module defines the following functions; each enters the '
+             'debugger\n'
+             'in a slightly different way:\n'
+             '\n'
+             'pdb.run(statement, globals=None, locals=None)\n'
+             '\n'
+             '   Execute the *statement* (given as a string or a code object) '
+             'under\n'
+             '   debugger control.  The debugger prompt appears before any '
+             'code is\n'
+             '   executed; you can set breakpoints and type "continue", or you '
+             'can\n'
+             '   step through the statement using "step" or "next" (all these\n'
+             '   commands are explained below).  The optional *globals* and '
+             '*locals*\n'
+             '   arguments specify the environment in which the code is '
+             'executed; by\n'
+             '   default the dictionary of the module "__main__" is used.  '
+             '(See the\n'
+             '   explanation of the built-in "exec()" or "eval()" functions.)\n'
+             '\n'
+             'pdb.runeval(expression, globals=None, locals=None)\n'
+             '\n'
+             '   Evaluate the *expression* (given as a string or a code '
+             'object)\n'
+             '   under debugger control.  When "runeval()" returns, it returns '
+             'the\n'
+             '   value of the expression.  Otherwise this function is similar '
+             'to\n'
+             '   "run()".\n'
+             '\n'
+             'pdb.runcall(function, *args, **kwds)\n'
+             '\n'
+             '   Call the *function* (a function or method object, not a '
+             'string)\n'
+             '   with the given arguments.  When "runcall()" returns, it '
+             'returns\n'
+             '   whatever the function call returned.  The debugger prompt '
+             'appears\n'
+             '   as soon as the function is entered.\n'
+             '\n'
+             'pdb.set_trace()\n'
+             '\n'
+             '   Enter the debugger at the calling stack frame.  This is '
+             'useful to\n'
+             '   hard-code a breakpoint at a given point in a program, even if '
+             'the\n'
+             '   code is not otherwise being debugged (e.g. when an assertion\n'
+             '   fails).\n'
+             '\n'
+             'pdb.post_mortem(traceback=None)\n'
+             '\n'
+             '   Enter post-mortem debugging of the given *traceback* object.  '
+             'If no\n'
+             '   *traceback* is given, it uses the one of the exception that '
+             'is\n'
+             '   currently being handled (an exception must be being handled '
+             'if the\n'
+             '   default is to be used).\n'
+             '\n'
+             'pdb.pm()\n'
+             '\n'
+             '   Enter post-mortem debugging of the traceback found in\n'
+             '   "sys.last_traceback".\n'
+             '\n'
+             'The "run*" functions and "set_trace()" are aliases for '
+             'instantiating\n'
+             'the "Pdb" class and calling the method of the same name.  If you '
+             'want\n'
+             'to access further features, you have to do this yourself:\n'
+             '\n'
+             "class pdb.Pdb(completekey='tab', stdin=None, stdout=None, "
+             'skip=None, nosigint=False, readrc=True)\n'
+             '\n'
+             '   "Pdb" is the debugger class.\n'
+             '\n'
+             '   The *completekey*, *stdin* and *stdout* arguments are passed '
+             'to the\n'
+             '   underlying "cmd.Cmd" class; see the description there.\n'
+             '\n'
+             '   The *skip* argument, if given, must be an iterable of '
+             'glob-style\n'
+             '   module name patterns.  The debugger will not step into frames '
+             'that\n'
+             '   originate in a module that matches one of these patterns. '
+             '[1]\n'
+             '\n'
+             '   By default, Pdb sets a handler for the SIGINT signal (which '
+             'is sent\n'
+             '   when the user presses "Ctrl-C" on the console) when you give '
+             'a\n'
+             '   "continue" command. This allows you to break into the '
+             'debugger\n'
+             '   again by pressing "Ctrl-C".  If you want Pdb not to touch '
+             'the\n'
+             '   SIGINT handler, set *nosigint* to true.\n'
+             '\n'
+             '   The *readrc* argument defaults to true and controls whether '
+             'Pdb\n'
+             '   will load .pdbrc files from the filesystem.\n'
+             '\n'
+             '   Example call to enable tracing with *skip*:\n'
+             '\n'
+             "      import pdb; pdb.Pdb(skip=['django.*']).set_trace()\n"
+             '\n'
+             '   New in version 3.1: The *skip* argument.\n'
+             '\n'
+             '   New in version 3.2: The *nosigint* argument.  Previously, a '
+             'SIGINT\n'
+             '   handler was never set by Pdb.\n'
+             '\n'
+             '   Changed in version 3.6: The *readrc* argument.\n'
+             '\n'
+             '   run(statement, globals=None, locals=None)\n'
+             '   runeval(expression, globals=None, locals=None)\n'
+             '   runcall(function, *args, **kwds)\n'
+             '   set_trace()\n'
+             '\n'
+             '      See the documentation for the functions explained above.\n'
+             '\n'
+             '\n'
+             'Debugger Commands\n'
+             '=================\n'
+             '\n'
+             'The commands recognized by the debugger are listed below.  Most\n'
+             'commands can be abbreviated to one or two letters as indicated; '
+             'e.g.\n'
+             '"h(elp)" means that either "h" or "help" can be used to enter '
+             'the help\n'
+             'command (but not "he" or "hel", nor "H" or "Help" or "HELP").\n'
+             'Arguments to commands must be separated by whitespace (spaces '
+             'or\n'
+             'tabs).  Optional arguments are enclosed in square brackets '
+             '("[]") in\n'
+             'the command syntax; the square brackets must not be typed.\n'
+             'Alternatives in the command syntax are separated by a vertical '
+             'bar\n'
+             '("|").\n'
+             '\n'
+             'Entering a blank line repeats the last command entered.  '
+             'Exception: if\n'
+             'the last command was a "list" command, the next 11 lines are '
+             'listed.\n'
+             '\n'
+             'Commands that the debugger doesn’t recognize are assumed to be '
+             'Python\n'
+             'statements and are executed in the context of the program being\n'
+             'debugged.  Python statements can also be prefixed with an '
+             'exclamation\n'
+             'point ("!").  This is a powerful way to inspect the program '
+             'being\n'
+             'debugged; it is even possible to change a variable or call a '
+             'function.\n'
+             'When an exception occurs in such a statement, the exception name '
+             'is\n'
+             'printed but the debugger’s state is not changed.\n'
+             '\n'
+             'The debugger supports aliases.  Aliases can have parameters '
+             'which\n'
+             'allows one a certain level of adaptability to the context under\n'
+             'examination.\n'
+             '\n'
+             'Multiple commands may be entered on a single line, separated by '
+             '";;".\n'
+             '(A single ";" is not used as it is the separator for multiple '
+             'commands\n'
+             'in a line that is passed to the Python parser.)  No intelligence '
+             'is\n'
+             'applied to separating the commands; the input is split at the '
+             'first\n'
+             '";;" pair, even if it is in the middle of a quoted string.\n'
+             '\n'
+             'If a file ".pdbrc" exists in the user’s home directory or in '
+             'the\n'
+             'current directory, it is read in and executed as if it had been '
+             'typed\n'
+             'at the debugger prompt.  This is particularly useful for '
+             'aliases.  If\n'
+             'both files exist, the one in the home directory is read first '
+             'and\n'
+             'aliases defined there can be overridden by the local file.\n'
+             '\n'
+             'Changed in version 3.2: ".pdbrc" can now contain commands that\n'
+             'continue debugging, such as "continue" or "next".  Previously, '
+             'these\n'
+             'commands had no effect.\n'
+             '\n'
+             'h(elp) [command]\n'
+             '\n'
+             '   Without argument, print the list of available commands.  With '
+             'a\n'
+             '   *command* as argument, print help about that command.  "help '
+             'pdb"\n'
+             '   displays the full documentation (the docstring of the "pdb"\n'
+             '   module).  Since the *command* argument must be an identifier, '
+             '"help\n'
+             '   exec" must be entered to get help on the "!" command.\n'
+             '\n'
+             'w(here)\n'
+             '\n'
+             '   Print a stack trace, with the most recent frame at the '
+             'bottom.  An\n'
+             '   arrow indicates the current frame, which determines the '
+             'context of\n'
+             '   most commands.\n'
+             '\n'
+             'd(own) [count]\n'
+             '\n'
+             '   Move the current frame *count* (default one) levels down in '
+             'the\n'
+             '   stack trace (to a newer frame).\n'
+             '\n'
+             'u(p) [count]\n'
+             '\n'
+             '   Move the current frame *count* (default one) levels up in the '
+             'stack\n'
+             '   trace (to an older frame).\n'
+             '\n'
+             'b(reak) [([filename:]lineno | function) [, condition]]\n'
+             '\n'
+             '   With a *lineno* argument, set a break there in the current '
+             'file.\n'
+             '   With a *function* argument, set a break at the first '
+             'executable\n'
+             '   statement within that function.  The line number may be '
+             'prefixed\n'
+             '   with a filename and a colon, to specify a breakpoint in '
+             'another\n'
+             '   file (probably one that hasn’t been loaded yet).  The file '
+             'is\n'
+             '   searched on "sys.path".  Note that each breakpoint is '
+             'assigned a\n'
+             '   number to which all the other breakpoint commands refer.\n'
+             '\n'
+             '   If a second argument is present, it is an expression which '
+             'must\n'
+             '   evaluate to true before the breakpoint is honored.\n'
+             '\n'
+             '   Without argument, list all breaks, including for each '
+             'breakpoint,\n'
+             '   the number of times that breakpoint has been hit, the '
+             'current\n'
+             '   ignore count, and the associated condition if any.\n'
+             '\n'
+             'tbreak [([filename:]lineno | function) [, condition]]\n'
+             '\n'
+             '   Temporary breakpoint, which is removed automatically when it '
+             'is\n'
+             '   first hit. The arguments are the same as for "break".\n'
+             '\n'
+             'cl(ear) [filename:lineno | bpnumber [bpnumber ...]]\n'
+             '\n'
+             '   With a *filename:lineno* argument, clear all the breakpoints '
+             'at\n'
+             '   this line. With a space separated list of breakpoint numbers, '
+             'clear\n'
+             '   those breakpoints. Without argument, clear all breaks (but '
+             'first\n'
+             '   ask confirmation).\n'
+             '\n'
+             'disable [bpnumber [bpnumber ...]]\n'
+             '\n'
+             '   Disable the breakpoints given as a space separated list of\n'
+             '   breakpoint numbers.  Disabling a breakpoint means it cannot '
+             'cause\n'
+             '   the program to stop execution, but unlike clearing a '
+             'breakpoint, it\n'
+             '   remains in the list of breakpoints and can be (re-)enabled.\n'
+             '\n'
+             'enable [bpnumber [bpnumber ...]]\n'
+             '\n'
+             '   Enable the breakpoints specified.\n'
+             '\n'
+             'ignore bpnumber [count]\n'
+             '\n'
+             '   Set the ignore count for the given breakpoint number.  If '
+             'count is\n'
+             '   omitted, the ignore count is set to 0.  A breakpoint becomes '
+             'active\n'
+             '   when the ignore count is zero.  When non-zero, the count is\n'
+             '   decremented each time the breakpoint is reached and the '
+             'breakpoint\n'
+             '   is not disabled and any associated condition evaluates to '
+             'true.\n'
+             '\n'
+             'condition bpnumber [condition]\n'
+             '\n'
+             '   Set a new *condition* for the breakpoint, an expression which '
+             'must\n'
+             '   evaluate to true before the breakpoint is honored.  If '
+             '*condition*\n'
+             '   is absent, any existing condition is removed; i.e., the '
+             'breakpoint\n'
+             '   is made unconditional.\n'
+             '\n'
+             'commands [bpnumber]\n'
+             '\n'
+             '   Specify a list of commands for breakpoint number *bpnumber*.  '
+             'The\n'
+             '   commands themselves appear on the following lines.  Type a '
+             'line\n'
+             '   containing just "end" to terminate the commands. An example:\n'
+             '\n'
+             '      (Pdb) commands 1\n'
+             '      (com) p some_variable\n'
+             '      (com) end\n'
+             '      (Pdb)\n'
+             '\n'
+             '   To remove all commands from a breakpoint, type commands and '
+             'follow\n'
+             '   it immediately with "end"; that is, give no commands.\n'
+             '\n'
+             '   With no *bpnumber* argument, commands refers to the last '
+             'breakpoint\n'
+             '   set.\n'
+             '\n'
+             '   You can use breakpoint commands to start your program up '
+             'again.\n'
+             '   Simply use the continue command, or step, or any other '
+             'command that\n'
+             '   resumes execution.\n'
+             '\n'
+             '   Specifying any command resuming execution (currently '
+             'continue,\n'
+             '   step, next, return, jump, quit and their abbreviations) '
+             'terminates\n'
+             '   the command list (as if that command was immediately followed '
+             'by\n'
+             '   end). This is because any time you resume execution (even '
+             'with a\n'
+             '   simple next or step), you may encounter another '
+             'breakpoint—which\n'
+             '   could have its own command list, leading to ambiguities about '
+             'which\n'
+             '   list to execute.\n'
+             '\n'
+             '   If you use the ‘silent’ command in the command list, the '
+             'usual\n'
+             '   message about stopping at a breakpoint is not printed.  This '
+             'may be\n'
+             '   desirable for breakpoints that are to print a specific '
+             'message and\n'
+             '   then continue.  If none of the other commands print anything, '
+             'you\n'
+             '   see no sign that the breakpoint was reached.\n'
+             '\n'
+             's(tep)\n'
+             '\n'
+             '   Execute the current line, stop at the first possible '
+             'occasion\n'
+             '   (either in a function that is called or on the next line in '
+             'the\n'
+             '   current function).\n'
+             '\n'
+             'n(ext)\n'
+             '\n'
+             '   Continue execution until the next line in the current '
+             'function is\n'
+             '   reached or it returns.  (The difference between "next" and '
+             '"step"\n'
+             '   is that "step" stops inside a called function, while "next"\n'
+             '   executes called functions at (nearly) full speed, only '
+             'stopping at\n'
+             '   the next line in the current function.)\n'
+             '\n'
+             'unt(il) [lineno]\n'
+             '\n'
+             '   Without argument, continue execution until the line with a '
+             'number\n'
+             '   greater than the current one is reached.\n'
+             '\n'
+             '   With a line number, continue execution until a line with a '
+             'number\n'
+             '   greater or equal to that is reached.  In both cases, also '
+             'stop when\n'
+             '   the current frame returns.\n'
+             '\n'
+             '   Changed in version 3.2: Allow giving an explicit line '
+             'number.\n'
+             '\n'
+             'r(eturn)\n'
+             '\n'
+             '   Continue execution until the current function returns.\n'
+             '\n'
+             'c(ont(inue))\n'
+             '\n'
+             '   Continue execution, only stop when a breakpoint is '
+             'encountered.\n'
+             '\n'
+             'j(ump) lineno\n'
+             '\n'
+             '   Set the next line that will be executed.  Only available in '
+             'the\n'
+             '   bottom-most frame.  This lets you jump back and execute code '
+             'again,\n'
+             '   or jump forward to skip code that you don’t want to run.\n'
+             '\n'
+             '   It should be noted that not all jumps are allowed – for '
+             'instance it\n'
+             '   is not possible to jump into the middle of a "for" loop or '
+             'out of a\n'
+             '   "finally" clause.\n'
+             '\n'
+             'l(ist) [first[, last]]\n'
+             '\n'
+             '   List source code for the current file.  Without arguments, '
+             'list 11\n'
+             '   lines around the current line or continue the previous '
+             'listing.\n'
+             '   With "." as argument, list 11 lines around the current line.  '
+             'With\n'
+             '   one argument, list 11 lines around at that line.  With two\n'
+             '   arguments, list the given range; if the second argument is '
+             'less\n'
+             '   than the first, it is interpreted as a count.\n'
+             '\n'
+             '   The current line in the current frame is indicated by "->".  '
+             'If an\n'
+             '   exception is being debugged, the line where the exception '
+             'was\n'
+             '   originally raised or propagated is indicated by ">>", if it '
+             'differs\n'
+             '   from the current line.\n'
+             '\n'
+             '   New in version 3.2: The ">>" marker.\n'
+             '\n'
+             'll | longlist\n'
+             '\n'
+             '   List all source code for the current function or frame.\n'
+             '   Interesting lines are marked as for "list".\n'
+             '\n'
+             '   New in version 3.2.\n'
+             '\n'
+             'a(rgs)\n'
+             '\n'
+             '   Print the argument list of the current function.\n'
+             '\n'
+             'p expression\n'
+             '\n'
+             '   Evaluate the *expression* in the current context and print '
+             'its\n'
+             '   value.\n'
+             '\n'
+             '   Note: "print()" can also be used, but is not a debugger '
+             'command —\n'
+             '     this executes the Python "print()" function.\n'
+             '\n'
+             'pp expression\n'
+             '\n'
+             '   Like the "p" command, except the value of the expression is '
+             'pretty-\n'
+             '   printed using the "pprint" module.\n'
+             '\n'
+             'whatis expression\n'
+             '\n'
+             '   Print the type of the *expression*.\n'
+             '\n'
+             'source expression\n'
+             '\n'
+             '   Try to get source code for the given object and display it.\n'
+             '\n'
+             '   New in version 3.2.\n'
+             '\n'
+             'display [expression]\n'
+             '\n'
+             '   Display the value of the expression if it changed, each time\n'
+             '   execution stops in the current frame.\n'
+             '\n'
+             '   Without expression, list all display expressions for the '
+             'current\n'
+             '   frame.\n'
+             '\n'
+             '   New in version 3.2.\n'
+             '\n'
+             'undisplay [expression]\n'
+             '\n'
+             '   Do not display the expression any more in the current frame.\n'
+             '   Without expression, clear all display expressions for the '
+             'current\n'
+             '   frame.\n'
+             '\n'
+             '   New in version 3.2.\n'
+             '\n'
+             'interact\n'
+             '\n'
+             '   Start an interactive interpreter (using the "code" module) '
+             'whose\n'
+             '   global namespace contains all the (global and local) names '
+             'found in\n'
+             '   the current scope.\n'
+             '\n'
+             '   New in version 3.2.\n'
+             '\n'
+             'alias [name [command]]\n'
+             '\n'
+             '   Create an alias called *name* that executes *command*.  The '
+             'command\n'
+             '   must *not* be enclosed in quotes.  Replaceable parameters can '
+             'be\n'
+             '   indicated by "%1", "%2", and so on, while "%*" is replaced by '
+             'all\n'
+             '   the parameters. If no command is given, the current alias '
+             'for\n'
+             '   *name* is shown. If no arguments are given, all aliases are '
+             'listed.\n'
+             '\n'
+             '   Aliases may be nested and can contain anything that can be '
+             'legally\n'
+             '   typed at the pdb prompt.  Note that internal pdb commands '
+             '*can* be\n'
+             '   overridden by aliases.  Such a command is then hidden until '
+             'the\n'
+             '   alias is removed.  Aliasing is recursively applied to the '
+             'first\n'
+             '   word of the command line; all other words in the line are '
+             'left\n'
+             '   alone.\n'
+             '\n'
+             '   As an example, here are two useful aliases (especially when '
+             'placed\n'
+             '   in the ".pdbrc" file):\n'
+             '\n'
+             '      # Print instance variables (usage "pi classInst")\n'
+             '      alias pi for k in %1.__dict__.keys(): '
+             'print("%1.",k,"=",%1.__dict__[k])\n'
+             '      # Print instance variables in self\n'
+             '      alias ps pi self\n'
+             '\n'
+             'unalias name\n'
+             '\n'
+             '   Delete the specified alias.\n'
+             '\n'
+             '! statement\n'
+             '\n'
+             '   Execute the (one-line) *statement* in the context of the '
+             'current\n'
+             '   stack frame. The exclamation point can be omitted unless the '
+             'first\n'
+             '   word of the statement resembles a debugger command.  To set '
+             'a\n'
+             '   global variable, you can prefix the assignment command with '
+             'a\n'
+             '   "global" statement on the same line, e.g.:\n'
+             '\n'
+             "      (Pdb) global list_options; list_options = ['-l']\n"
+             '      (Pdb)\n'
+             '\n'
+             'run [args ...]\n'
+             'restart [args ...]\n'
+             '\n'
+             '   Restart the debugged Python program.  If an argument is '
+             'supplied,\n'
+             '   it is split with "shlex" and the result is used as the new\n'
+             '   "sys.argv". History, breakpoints, actions and debugger '
+             'options are\n'
+             '   preserved. "restart" is an alias for "run".\n'
+             '\n'
+             'q(uit)\n'
+             '\n'
+             '   Quit from the debugger.  The program being executed is '
+             'aborted.\n'
+             '\n'
+             '-[ Footnotes ]-\n'
+             '\n'
+             '[1] Whether a frame is considered to originate in a certain '
+             'module\n'
+             '    is determined by the "__name__" in the frame globals.\n',
+ 'del': 'The "del" statement\n'
+        '*******************\n'
+        '\n'
+        '   del_stmt ::= "del" target_list\n'
+        '\n'
+        'Deletion is recursively defined very similar to the way assignment '
+        'is\n'
+        'defined. Rather than spelling it out in full details, here are some\n'
+        'hints.\n'
+        '\n'
+        'Deletion of a target list recursively deletes each target, from left\n'
+        'to right.\n'
+        '\n'
+        'Deletion of a name removes the binding of that name from the local '
+        'or\n'
+        'global namespace, depending on whether the name occurs in a "global"\n'
+        'statement in the same code block.  If the name is unbound, a\n'
+        '"NameError" exception will be raised.\n'
+        '\n'
+        'Deletion of attribute references, subscriptions and slicings is '
+        'passed\n'
+        'to the primary object involved; deletion of a slicing is in general\n'
+        'equivalent to assignment of an empty slice of the right type (but '
+        'even\n'
+        'this is determined by the sliced object).\n'
+        '\n'
+        'Changed in version 3.2: Previously it was illegal to delete a name\n'
+        'from the local namespace if it occurs as a free variable in a nested\n'
+        'block.\n',
+ 'dict': 'Dictionary displays\n'
+         '*******************\n'
+         '\n'
+         'A dictionary display is a possibly empty series of key/datum pairs\n'
+         'enclosed in curly braces:\n'
+         '\n'
+         '   dict_display       ::= "{" [key_datum_list | dict_comprehension] '
+         '"}"\n'
+         '   key_datum_list     ::= key_datum ("," key_datum)* [","]\n'
+         '   key_datum          ::= expression ":" expression | "**" or_expr\n'
+         '   dict_comprehension ::= expression ":" expression comp_for\n'
+         '\n'
+         'A dictionary display yields a new dictionary object.\n'
+         '\n'
+         'If a comma-separated sequence of key/datum pairs is given, they are\n'
+         'evaluated from left to right to define the entries of the '
+         'dictionary:\n'
+         'each key object is used as a key into the dictionary to store the\n'
+         'corresponding datum.  This means that you can specify the same key\n'
+         'multiple times in the key/datum list, and the final dictionary’s '
+         'value\n'
+         'for that key will be the last one given.\n'
+         '\n'
+         'A double asterisk "**" denotes *dictionary unpacking*. Its operand\n'
+         'must be a *mapping*.  Each mapping item is added to the new\n'
+         'dictionary.  Later values replace values already set by earlier\n'
+         'key/datum pairs and earlier dictionary unpackings.\n'
+         '\n'
+         'New in version 3.5: Unpacking into dictionary displays, originally\n'
+         'proposed by **PEP 448**.\n'
+         '\n'
+         'A dict comprehension, in contrast to list and set comprehensions,\n'
+         'needs two expressions separated with a colon followed by the usual\n'
+         '“for” and “if” clauses. When the comprehension is run, the '
+         'resulting\n'
+         'key and value elements are inserted in the new dictionary in the '
+         'order\n'
+         'they are produced.\n'
+         '\n'
+         'Restrictions on the types of the key values are listed earlier in\n'
+         'section The standard type hierarchy.  (To summarize, the key type\n'
+         'should be *hashable*, which excludes all mutable objects.)  Clashes\n'
+         'between duplicate keys are not detected; the last datum (textually\n'
+         'rightmost in the display) stored for a given key value prevails.\n',
+ 'dynamic-features': 'Interaction with dynamic features\n'
+                     '*********************************\n'
+                     '\n'
+                     'Name resolution of free variables occurs at runtime, not '
+                     'at compile\n'
+                     'time. This means that the following code will print 42:\n'
+                     '\n'
+                     '   i = 10\n'
+                     '   def f():\n'
+                     '       print(i)\n'
+                     '   i = 42\n'
+                     '   f()\n'
+                     '\n'
+                     'The "eval()" and "exec()" functions do not have access '
+                     'to the full\n'
+                     'environment for resolving names.  Names may be resolved '
+                     'in the local\n'
+                     'and global namespaces of the caller.  Free variables are '
+                     'not resolved\n'
+                     'in the nearest enclosing namespace, but in the global '
+                     'namespace.  [1]\n'
+                     'The "exec()" and "eval()" functions have optional '
+                     'arguments to\n'
+                     'override the global and local namespace.  If only one '
+                     'namespace is\n'
+                     'specified, it is used for both.\n',
+ 'else': 'The "if" statement\n'
+         '******************\n'
+         '\n'
+         'The "if" statement is used for conditional execution:\n'
+         '\n'
+         '   if_stmt ::= "if" expression ":" suite\n'
+         '               ("elif" expression ":" suite)*\n'
+         '               ["else" ":" suite]\n'
+         '\n'
+         'It selects exactly one of the suites by evaluating the expressions '
+         'one\n'
+         'by one until one is found to be true (see section Boolean '
+         'operations\n'
+         'for the definition of true and false); then that suite is executed\n'
+         '(and no other part of the "if" statement is executed or evaluated).\n'
+         'If all expressions are false, the suite of the "else" clause, if\n'
+         'present, is executed.\n',
+ 'exceptions': 'Exceptions\n'
+               '**********\n'
+               '\n'
+               'Exceptions are a means of breaking out of the normal flow of '
+               'control\n'
+               'of a code block in order to handle errors or other '
+               'exceptional\n'
+               'conditions.  An exception is *raised* at the point where the '
+               'error is\n'
+               'detected; it may be *handled* by the surrounding code block or '
+               'by any\n'
+               'code block that directly or indirectly invoked the code block '
+               'where\n'
+               'the error occurred.\n'
+               '\n'
+               'The Python interpreter raises an exception when it detects a '
+               'run-time\n'
+               'error (such as division by zero).  A Python program can also\n'
+               'explicitly raise an exception with the "raise" statement. '
+               'Exception\n'
+               'handlers are specified with the "try" … "except" statement.  '
+               'The\n'
+               '"finally" clause of such a statement can be used to specify '
+               'cleanup\n'
+               'code which does not handle the exception, but is executed '
+               'whether an\n'
+               'exception occurred or not in the preceding code.\n'
+               '\n'
+               'Python uses the “termination” model of error handling: an '
+               'exception\n'
+               'handler can find out what happened and continue execution at '
+               'an outer\n'
+               'level, but it cannot repair the cause of the error and retry '
+               'the\n'
+               'failing operation (except by re-entering the offending piece '
+               'of code\n'
+               'from the top).\n'
+               '\n'
+               'When an exception is not handled at all, the interpreter '
+               'terminates\n'
+               'execution of the program, or returns to its interactive main '
+               'loop.  In\n'
+               'either case, it prints a stack backtrace, except when the '
+               'exception is\n'
+               '"SystemExit".\n'
+               '\n'
+               'Exceptions are identified by class instances.  The "except" '
+               'clause is\n'
+               'selected depending on the class of the instance: it must '
+               'reference the\n'
+               'class of the instance or a base class thereof.  The instance '
+               'can be\n'
+               'received by the handler and can carry additional information '
+               'about the\n'
+               'exceptional condition.\n'
+               '\n'
+               'Note: Exception messages are not part of the Python API.  '
+               'Their\n'
+               '  contents may change from one version of Python to the next '
+               'without\n'
+               '  warning and should not be relied on by code which will run '
+               'under\n'
+               '  multiple versions of the interpreter.\n'
+               '\n'
+               'See also the description of the "try" statement in section The '
+               'try\n'
+               'statement and "raise" statement in section The raise '
+               'statement.\n'
+               '\n'
+               '-[ Footnotes ]-\n'
+               '\n'
+               '[1] This limitation occurs because the code that is executed '
+               'by\n'
+               '    these operations is not available at the time the module '
+               'is\n'
+               '    compiled.\n',
+ 'execmodel': 'Execution model\n'
+              '***************\n'
+              '\n'
+              '\n'
+              'Structure of a program\n'
+              '======================\n'
+              '\n'
+              'A Python program is constructed from code blocks. A *block* is '
+              'a piece\n'
+              'of Python program text that is executed as a unit. The '
+              'following are\n'
+              'blocks: a module, a function body, and a class definition. '
+              'Each\n'
+              'command typed interactively is a block.  A script file (a file '
+              'given\n'
+              'as standard input to the interpreter or specified as a command '
+              'line\n'
+              'argument to the interpreter) is a code block.  A script command '
+              '(a\n'
+              'command specified on the interpreter command line with the '
+              '"-c"\n'
+              'option) is a code block.  The string argument passed to the '
+              'built-in\n'
+              'functions "eval()" and "exec()" is a code block.\n'
+              '\n'
+              'A code block is executed in an *execution frame*.  A frame '
+              'contains\n'
+              'some administrative information (used for debugging) and '
+              'determines\n'
+              'where and how execution continues after the code block’s '
+              'execution has\n'
+              'completed.\n'
+              '\n'
+              '\n'
+              'Naming and binding\n'
+              '==================\n'
+              '\n'
+              '\n'
+              'Binding of names\n'
+              '----------------\n'
+              '\n'
+              '*Names* refer to objects.  Names are introduced by name '
+              'binding\n'
+              'operations.\n'
+              '\n'
+              'The following constructs bind names: formal parameters to '
+              'functions,\n'
+              '"import" statements, class and function definitions (these bind '
+              'the\n'
+              'class or function name in the defining block), and targets that '
+              'are\n'
+              'identifiers if occurring in an assignment, "for" loop header, '
+              'or after\n'
+              '"as" in a "with" statement or "except" clause. The "import" '
+              'statement\n'
+              'of the form "from ... import *" binds all names defined in the\n'
+              'imported module, except those beginning with an underscore.  '
+              'This form\n'
+              'may only be used at the module level.\n'
+              '\n'
+              'A target occurring in a "del" statement is also considered '
+              'bound for\n'
+              'this purpose (though the actual semantics are to unbind the '
+              'name).\n'
+              '\n'
+              'Each assignment or import statement occurs within a block '
+              'defined by a\n'
+              'class or function definition or at the module level (the '
+              'top-level\n'
+              'code block).\n'
+              '\n'
+              'If a name is bound in a block, it is a local variable of that '
+              'block,\n'
+              'unless declared as "nonlocal" or "global".  If a name is bound '
+              'at the\n'
+              'module level, it is a global variable.  (The variables of the '
+              'module\n'
+              'code block are local and global.)  If a variable is used in a '
+              'code\n'
+              'block but not defined there, it is a *free variable*.\n'
+              '\n'
+              'Each occurrence of a name in the program text refers to the '
+              '*binding*\n'
+              'of that name established by the following name resolution '
+              'rules.\n'
+              '\n'
+              '\n'
+              'Resolution of names\n'
+              '-------------------\n'
+              '\n'
+              'A *scope* defines the visibility of a name within a block.  If '
+              'a local\n'
+              'variable is defined in a block, its scope includes that block.  '
+              'If the\n'
+              'definition occurs in a function block, the scope extends to any '
+              'blocks\n'
+              'contained within the defining one, unless a contained block '
+              'introduces\n'
+              'a different binding for the name.\n'
+              '\n'
+              'When a name is used in a code block, it is resolved using the '
+              'nearest\n'
+              'enclosing scope.  The set of all such scopes visible to a code '
+              'block\n'
+              'is called the block’s *environment*.\n'
+              '\n'
+              'When a name is not found at all, a "NameError" exception is '
+              'raised. If\n'
+              'the current scope is a function scope, and the name refers to a '
+              'local\n'
+              'variable that has not yet been bound to a value at the point '
+              'where the\n'
+              'name is used, an "UnboundLocalError" exception is raised.\n'
+              '"UnboundLocalError" is a subclass of "NameError".\n'
+              '\n'
+              'If a name binding operation occurs anywhere within a code '
+              'block, all\n'
+              'uses of the name within the block are treated as references to '
+              'the\n'
+              'current block.  This can lead to errors when a name is used '
+              'within a\n'
+              'block before it is bound.  This rule is subtle.  Python lacks\n'
+              'declarations and allows name binding operations to occur '
+              'anywhere\n'
+              'within a code block.  The local variables of a code block can '
+              'be\n'
+              'determined by scanning the entire text of the block for name '
+              'binding\n'
+              'operations.\n'
+              '\n'
+              'If the "global" statement occurs within a block, all uses of '
+              'the name\n'
+              'specified in the statement refer to the binding of that name in '
+              'the\n'
+              'top-level namespace.  Names are resolved in the top-level '
+              'namespace by\n'
+              'searching the global namespace, i.e. the namespace of the '
+              'module\n'
+              'containing the code block, and the builtins namespace, the '
+              'namespace\n'
+              'of the module "builtins".  The global namespace is searched '
+              'first.  If\n'
+              'the name is not found there, the builtins namespace is '
+              'searched.  The\n'
+              '"global" statement must precede all uses of the name.\n'
+              '\n'
+              'The "global" statement has the same scope as a name binding '
+              'operation\n'
+              'in the same block.  If the nearest enclosing scope for a free '
+              'variable\n'
+              'contains a global statement, the free variable is treated as a '
+              'global.\n'
+              '\n'
+              'The "nonlocal" statement causes corresponding names to refer '
+              'to\n'
+              'previously bound variables in the nearest enclosing function '
+              'scope.\n'
+              '"SyntaxError" is raised at compile time if the given name does '
+              'not\n'
+              'exist in any enclosing function scope.\n'
+              '\n'
+              'The namespace for a module is automatically created the first '
+              'time a\n'
+              'module is imported.  The main module for a script is always '
+              'called\n'
+              '"__main__".\n'
+              '\n'
+              'Class definition blocks and arguments to "exec()" and "eval()" '
+              'are\n'
+              'special in the context of name resolution. A class definition '
+              'is an\n'
+              'executable statement that may use and define names. These '
+              'references\n'
+              'follow the normal rules for name resolution with an exception '
+              'that\n'
+              'unbound local variables are looked up in the global namespace. '
+              'The\n'
+              'namespace of the class definition becomes the attribute '
+              'dictionary of\n'
+              'the class. The scope of names defined in a class block is '
+              'limited to\n'
+              'the class block; it does not extend to the code blocks of '
+              'methods –\n'
+              'this includes comprehensions and generator expressions since '
+              'they are\n'
+              'implemented using a function scope.  This means that the '
+              'following\n'
+              'will fail:\n'
+              '\n'
+              '   class A:\n'
+              '       a = 42\n'
+              '       b = list(a + i for i in range(10))\n'
+              '\n'
+              '\n'
+              'Builtins and restricted execution\n'
+              '---------------------------------\n'
+              '\n'
+              '**CPython implementation detail:** Users should not touch\n'
+              '"__builtins__"; it is strictly an implementation detail.  '
+              'Users\n'
+              'wanting to override values in the builtins namespace should '
+              '"import"\n'
+              'the "builtins" module and modify its attributes appropriately.\n'
+              '\n'
+              'The builtins namespace associated with the execution of a code '
+              'block\n'
+              'is actually found by looking up the name "__builtins__" in its '
+              'global\n'
+              'namespace; this should be a dictionary or a module (in the '
+              'latter case\n'
+              'the module’s dictionary is used).  By default, when in the '
+              '"__main__"\n'
+              'module, "__builtins__" is the built-in module "builtins"; when '
+              'in any\n'
+              'other module, "__builtins__" is an alias for the dictionary of '
+              'the\n'
+              '"builtins" module itself.\n'
+              '\n'
+              '\n'
+              'Interaction with dynamic features\n'
+              '---------------------------------\n'
+              '\n'
+              'Name resolution of free variables occurs at runtime, not at '
+              'compile\n'
+              'time. This means that the following code will print 42:\n'
+              '\n'
+              '   i = 10\n'
+              '   def f():\n'
+              '       print(i)\n'
+              '   i = 42\n'
+              '   f()\n'
+              '\n'
+              'The "eval()" and "exec()" functions do not have access to the '
+              'full\n'
+              'environment for resolving names.  Names may be resolved in the '
+              'local\n'
+              'and global namespaces of the caller.  Free variables are not '
+              'resolved\n'
+              'in the nearest enclosing namespace, but in the global '
+              'namespace.  [1]\n'
+              'The "exec()" and "eval()" functions have optional arguments to\n'
+              'override the global and local namespace.  If only one namespace '
+              'is\n'
+              'specified, it is used for both.\n'
+              '\n'
+              '\n'
+              'Exceptions\n'
+              '==========\n'
+              '\n'
+              'Exceptions are a means of breaking out of the normal flow of '
+              'control\n'
+              'of a code block in order to handle errors or other exceptional\n'
+              'conditions.  An exception is *raised* at the point where the '
+              'error is\n'
+              'detected; it may be *handled* by the surrounding code block or '
+              'by any\n'
+              'code block that directly or indirectly invoked the code block '
+              'where\n'
+              'the error occurred.\n'
+              '\n'
+              'The Python interpreter raises an exception when it detects a '
+              'run-time\n'
+              'error (such as division by zero).  A Python program can also\n'
+              'explicitly raise an exception with the "raise" statement. '
+              'Exception\n'
+              'handlers are specified with the "try" … "except" statement.  '
+              'The\n'
+              '"finally" clause of such a statement can be used to specify '
+              'cleanup\n'
+              'code which does not handle the exception, but is executed '
+              'whether an\n'
+              'exception occurred or not in the preceding code.\n'
+              '\n'
+              'Python uses the “termination” model of error handling: an '
+              'exception\n'
+              'handler can find out what happened and continue execution at an '
+              'outer\n'
+              'level, but it cannot repair the cause of the error and retry '
+              'the\n'
+              'failing operation (except by re-entering the offending piece of '
+              'code\n'
+              'from the top).\n'
+              '\n'
+              'When an exception is not handled at all, the interpreter '
+              'terminates\n'
+              'execution of the program, or returns to its interactive main '
+              'loop.  In\n'
+              'either case, it prints a stack backtrace, except when the '
+              'exception is\n'
+              '"SystemExit".\n'
+              '\n'
+              'Exceptions are identified by class instances.  The "except" '
+              'clause is\n'
+              'selected depending on the class of the instance: it must '
+              'reference the\n'
+              'class of the instance or a base class thereof.  The instance '
+              'can be\n'
+              'received by the handler and can carry additional information '
+              'about the\n'
+              'exceptional condition.\n'
+              '\n'
+              'Note: Exception messages are not part of the Python API.  '
+              'Their\n'
+              '  contents may change from one version of Python to the next '
+              'without\n'
+              '  warning and should not be relied on by code which will run '
+              'under\n'
+              '  multiple versions of the interpreter.\n'
+              '\n'
+              'See also the description of the "try" statement in section The '
+              'try\n'
+              'statement and "raise" statement in section The raise '
+              'statement.\n'
+              '\n'
+              '-[ Footnotes ]-\n'
+              '\n'
+              '[1] This limitation occurs because the code that is executed '
+              'by\n'
+              '    these operations is not available at the time the module '
+              'is\n'
+              '    compiled.\n',
+ 'exprlists': 'Expression lists\n'
+              '****************\n'
+              '\n'
+              '   expression_list    ::= expression ("," expression)* [","]\n'
+              '   starred_list       ::= starred_item ("," starred_item)* '
+              '[","]\n'
+              '   starred_expression ::= expression | (starred_item ",")* '
+              '[starred_item]\n'
+              '   starred_item       ::= expression | "*" or_expr\n'
+              '\n'
+              'Except when part of a list or set display, an expression list\n'
+              'containing at least one comma yields a tuple.  The length of '
+              'the tuple\n'
+              'is the number of expressions in the list.  The expressions are\n'
+              'evaluated from left to right.\n'
+              '\n'
+              'An asterisk "*" denotes *iterable unpacking*.  Its operand must '
+              'be an\n'
+              '*iterable*.  The iterable is expanded into a sequence of items, '
+              'which\n'
+              'are included in the new tuple, list, or set, at the site of '
+              'the\n'
+              'unpacking.\n'
+              '\n'
+              'New in version 3.5: Iterable unpacking in expression lists, '
+              'originally\n'
+              'proposed by **PEP 448**.\n'
+              '\n'
+              'The trailing comma is required only to create a single tuple '
+              '(a.k.a. a\n'
+              '*singleton*); it is optional in all other cases.  A single '
+              'expression\n'
+              'without a trailing comma doesn’t create a tuple, but rather '
+              'yields the\n'
+              'value of that expression. (To create an empty tuple, use an '
+              'empty pair\n'
+              'of parentheses: "()".)\n',
+ 'floating': 'Floating point literals\n'
+             '***********************\n'
+             '\n'
+             'Floating point literals are described by the following lexical\n'
+             'definitions:\n'
+             '\n'
+             '   floatnumber   ::= pointfloat | exponentfloat\n'
+             '   pointfloat    ::= [digitpart] fraction | digitpart "."\n'
+             '   exponentfloat ::= (digitpart | pointfloat) exponent\n'
+             '   digitpart     ::= digit (["_"] digit)*\n'
+             '   fraction      ::= "." digitpart\n'
+             '   exponent      ::= ("e" | "E") ["+" | "-"] digitpart\n'
+             '\n'
+             'Note that the integer and exponent parts are always interpreted '
+             'using\n'
+             'radix 10. For example, "077e010" is legal, and denotes the same '
+             'number\n'
+             'as "77e10". The allowed range of floating point literals is\n'
+             'implementation-dependent.  As in integer literals, underscores '
+             'are\n'
+             'supported for digit grouping.\n'
+             '\n'
+             'Some examples of floating point literals:\n'
+             '\n'
+             '   3.14    10.    .001    1e100    3.14e-10    0e0    '
+             '3.14_15_93\n'
+             '\n'
+             'Changed in version 3.6: Underscores are now allowed for '
+             'grouping\n'
+             'purposes in literals.\n',
+ 'for': 'The "for" statement\n'
+        '*******************\n'
+        '\n'
+        'The "for" statement is used to iterate over the elements of a '
+        'sequence\n'
+        '(such as a string, tuple or list) or other iterable object:\n'
+        '\n'
+        '   for_stmt ::= "for" target_list "in" expression_list ":" suite\n'
+        '                ["else" ":" suite]\n'
+        '\n'
+        'The expression list is evaluated once; it should yield an iterable\n'
+        'object.  An iterator is created for the result of the\n'
+        '"expression_list".  The suite is then executed once for each item\n'
+        'provided by the iterator, in the order returned by the iterator.  '
+        'Each\n'
+        'item in turn is assigned to the target list using the standard rules\n'
+        'for assignments (see Assignment statements), and then the suite is\n'
+        'executed.  When the items are exhausted (which is immediately when '
+        'the\n'
+        'sequence is empty or an iterator raises a "StopIteration" '
+        'exception),\n'
+        'the suite in the "else" clause, if present, is executed, and the '
+        'loop\n'
+        'terminates.\n'
+        '\n'
+        'A "break" statement executed in the first suite terminates the loop\n'
+        'without executing the "else" clause’s suite.  A "continue" statement\n'
+        'executed in the first suite skips the rest of the suite and '
+        'continues\n'
+        'with the next item, or with the "else" clause if there is no next\n'
+        'item.\n'
+        '\n'
+        'The for-loop makes assignments to the variables(s) in the target '
+        'list.\n'
+        'This overwrites all previous assignments to those variables '
+        'including\n'
+        'those made in the suite of the for-loop:\n'
+        '\n'
+        '   for i in range(10):\n'
+        '       print(i)\n'
+        '       i = 5             # this will not affect the for-loop\n'
+        '                         # because i will be overwritten with the '
+        'next\n'
+        '                         # index in the range\n'
+        '\n'
+        'Names in the target list are not deleted when the loop is finished,\n'
+        'but if the sequence is empty, they will not have been assigned to at\n'
+        'all by the loop.  Hint: the built-in function "range()" returns an\n'
+        'iterator of integers suitable to emulate the effect of Pascal’s "for '
+        'i\n'
+        ':= a to b do"; e.g., "list(range(3))" returns the list "[0, 1, 2]".\n'
+        '\n'
+        'Note: There is a subtlety when the sequence is being modified by the\n'
+        '  loop (this can only occur for mutable sequences, e.g. lists).  An\n'
+        '  internal counter is used to keep track of which item is used next,\n'
+        '  and this is incremented on each iteration.  When this counter has\n'
+        '  reached the length of the sequence the loop terminates.  This '
+        'means\n'
+        '  that if the suite deletes the current (or a previous) item from '
+        'the\n'
+        '  sequence, the next item will be skipped (since it gets the index '
+        'of\n'
+        '  the current item which has already been treated).  Likewise, if '
+        'the\n'
+        '  suite inserts an item in the sequence before the current item, the\n'
+        '  current item will be treated again the next time through the loop.\n'
+        '  This can lead to nasty bugs that can be avoided by making a\n'
+        '  temporary copy using a slice of the whole sequence, e.g.,\n'
+        '\n'
+        '     for x in a[:]:\n'
+        '         if x < 0: a.remove(x)\n',
+ 'formatstrings': 'Format String Syntax\n'
+                  '********************\n'
+                  '\n'
+                  'The "str.format()" method and the "Formatter" class share '
+                  'the same\n'
+                  'syntax for format strings (although in the case of '
+                  '"Formatter",\n'
+                  'subclasses can define their own format string syntax).  The '
+                  'syntax is\n'
+                  'related to that of formatted string literals, but there '
+                  'are\n'
+                  'differences.\n'
+                  '\n'
+                  'Format strings contain “replacement fields” surrounded by '
+                  'curly braces\n'
+                  '"{}". Anything that is not contained in braces is '
+                  'considered literal\n'
+                  'text, which is copied unchanged to the output.  If you need '
+                  'to include\n'
+                  'a brace character in the literal text, it can be escaped by '
+                  'doubling:\n'
+                  '"{{" and "}}".\n'
+                  '\n'
+                  'The grammar for a replacement field is as follows:\n'
+                  '\n'
+                  '      replacement_field ::= "{" [field_name] ["!" '
+                  'conversion] [":" format_spec] "}"\n'
+                  '      field_name        ::= arg_name ("." attribute_name | '
+                  '"[" element_index "]")*\n'
+                  '      arg_name          ::= [identifier | digit+]\n'
+                  '      attribute_name    ::= identifier\n'
+                  '      element_index     ::= digit+ | index_string\n'
+                  '      index_string      ::= <any source character except '
+                  '"]"> +\n'
+                  '      conversion        ::= "r" | "s" | "a"\n'
+                  '      format_spec       ::= <described in the next '
+                  'section>\n'
+                  '\n'
+                  'In less formal terms, the replacement field can start with '
+                  'a\n'
+                  '*field_name* that specifies the object whose value is to be '
+                  'formatted\n'
+                  'and inserted into the output instead of the replacement '
+                  'field. The\n'
+                  '*field_name* is optionally followed by a  *conversion* '
+                  'field, which is\n'
+                  'preceded by an exclamation point "\'!\'", and a '
+                  '*format_spec*, which is\n'
+                  'preceded by a colon "\':\'".  These specify a non-default '
+                  'format for the\n'
+                  'replacement value.\n'
+                  '\n'
+                  'See also the Format Specification Mini-Language section.\n'
+                  '\n'
+                  'The *field_name* itself begins with an *arg_name* that is '
+                  'either a\n'
+                  'number or a keyword.  If it’s a number, it refers to a '
+                  'positional\n'
+                  'argument, and if it’s a keyword, it refers to a named '
+                  'keyword\n'
+                  'argument.  If the numerical arg_names in a format string '
+                  'are 0, 1, 2,\n'
+                  '… in sequence, they can all be omitted (not just some) and '
+                  'the numbers\n'
+                  '0, 1, 2, … will be automatically inserted in that order. '
+                  'Because\n'
+                  '*arg_name* is not quote-delimited, it is not possible to '
+                  'specify\n'
+                  'arbitrary dictionary keys (e.g., the strings "\'10\'" or '
+                  '"\':-]\'") within\n'
+                  'a format string. The *arg_name* can be followed by any '
+                  'number of index\n'
+                  'or attribute expressions. An expression of the form '
+                  '"\'.name\'" selects\n'
+                  'the named attribute using "getattr()", while an expression '
+                  'of the form\n'
+                  '"\'[index]\'" does an index lookup using "__getitem__()".\n'
+                  '\n'
+                  'Changed in version 3.1: The positional argument specifiers '
+                  'can be\n'
+                  'omitted for "str.format()", so "\'{} {}\'.format(a, b)" is '
+                  'equivalent to\n'
+                  '"\'{0} {1}\'.format(a, b)".\n'
+                  '\n'
+                  'Changed in version 3.4: The positional argument specifiers '
+                  'can be\n'
+                  'omitted for "Formatter".\n'
+                  '\n'
+                  'Some simple format string examples:\n'
+                  '\n'
+                  '   "First, thou shalt count to {0}"  # References first '
+                  'positional argument\n'
+                  '   "Bring me a {}"                   # Implicitly '
+                  'references the first positional argument\n'
+                  '   "From {} to {}"                   # Same as "From {0} to '
+                  '{1}"\n'
+                  '   "My quest is {name}"              # References keyword '
+                  "argument 'name'\n"
+                  '   "Weight in tons {0.weight}"       # \'weight\' attribute '
+                  'of first positional arg\n'
+                  '   "Units destroyed: {players[0]}"   # First element of '
+                  "keyword argument 'players'.\n"
+                  '\n'
+                  'The *conversion* field causes a type coercion before '
+                  'formatting.\n'
+                  'Normally, the job of formatting a value is done by the '
+                  '"__format__()"\n'
+                  'method of the value itself.  However, in some cases it is '
+                  'desirable to\n'
+                  'force a type to be formatted as a string, overriding its '
+                  'own\n'
+                  'definition of formatting.  By converting the value to a '
+                  'string before\n'
+                  'calling "__format__()", the normal formatting logic is '
+                  'bypassed.\n'
+                  '\n'
+                  'Three conversion flags are currently supported: "\'!s\'" '
+                  'which calls\n'
+                  '"str()" on the value, "\'!r\'" which calls "repr()" and '
+                  '"\'!a\'" which\n'
+                  'calls "ascii()".\n'
+                  '\n'
+                  'Some examples:\n'
+                  '\n'
+                  '   "Harold\'s a clever {0!s}"        # Calls str() on the '
+                  'argument first\n'
+                  '   "Bring out the holy {name!r}"    # Calls repr() on the '
+                  'argument first\n'
+                  '   "More {!a}"                      # Calls ascii() on the '
+                  'argument first\n'
+                  '\n'
+                  'The *format_spec* field contains a specification of how the '
+                  'value\n'
+                  'should be presented, including such details as field width, '
+                  'alignment,\n'
+                  'padding, decimal precision and so on.  Each value type can '
+                  'define its\n'
+                  'own “formatting mini-language” or interpretation of the '
+                  '*format_spec*.\n'
+                  '\n'
+                  'Most built-in types support a common formatting '
+                  'mini-language, which\n'
+                  'is described in the next section.\n'
+                  '\n'
+                  'A *format_spec* field can also include nested replacement '
+                  'fields\n'
+                  'within it. These nested replacement fields may contain a '
+                  'field name,\n'
+                  'conversion flag and format specification, but deeper '
+                  'nesting is not\n'
+                  'allowed.  The replacement fields within the format_spec '
+                  'are\n'
+                  'substituted before the *format_spec* string is interpreted. '
+                  'This\n'
+                  'allows the formatting of a value to be dynamically '
+                  'specified.\n'
+                  '\n'
+                  'See the Format examples section for some examples.\n'
+                  '\n'
+                  '\n'
+                  'Format Specification Mini-Language\n'
+                  '==================================\n'
+                  '\n'
+                  '“Format specifications” are used within replacement fields '
+                  'contained\n'
+                  'within a format string to define how individual values are '
+                  'presented\n'
+                  '(see Format String Syntax and Formatted string literals). '
+                  'They can\n'
+                  'also be passed directly to the built-in "format()" '
+                  'function.  Each\n'
+                  'formattable type may define how the format specification is '
+                  'to be\n'
+                  'interpreted.\n'
+                  '\n'
+                  'Most built-in types implement the following options for '
+                  'format\n'
+                  'specifications, although some of the formatting options are '
+                  'only\n'
+                  'supported by the numeric types.\n'
+                  '\n'
+                  'A general convention is that an empty format string ("""") '
+                  'produces\n'
+                  'the same result as if you had called "str()" on the value. '
+                  'A non-empty\n'
+                  'format string typically modifies the result.\n'
+                  '\n'
+                  'The general form of a *standard format specifier* is:\n'
+                  '\n'
+                  '   format_spec     ::= '
+                  '[[fill]align][sign][#][0][width][grouping_option][.precision][type]\n'
+                  '   fill            ::= <any character>\n'
+                  '   align           ::= "<" | ">" | "=" | "^"\n'
+                  '   sign            ::= "+" | "-" | " "\n'
+                  '   width           ::= digit+\n'
+                  '   grouping_option ::= "_" | ","\n'
+                  '   precision       ::= digit+\n'
+                  '   type            ::= "b" | "c" | "d" | "e" | "E" | "f" | '
+                  '"F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"\n'
+                  '\n'
+                  'If a valid *align* value is specified, it can be preceded '
+                  'by a *fill*\n'
+                  'character that can be any character and defaults to a space '
+                  'if\n'
+                  'omitted. It is not possible to use a literal curly brace '
+                  '(“"{"” or\n'
+                  '“"}"”) as the *fill* character in a formatted string '
+                  'literal or when\n'
+                  'using the "str.format()" method.  However, it is possible '
+                  'to insert a\n'
+                  'curly brace with a nested replacement field.  This '
+                  'limitation doesn’t\n'
+                  'affect the "format()" function.\n'
+                  '\n'
+                  'The meaning of the various alignment options is as '
+                  'follows:\n'
+                  '\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | Option    | '
+                  'Meaning                                                    '
+                  '|\n'
+                  '   '
+                  '+===========+============================================================+\n'
+                  '   | "\'<\'"     | Forces the field to be left-aligned '
+                  'within the available   |\n'
+                  '   |           | space (this is the default for most '
+                  'objects).              |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'>\'"     | Forces the field to be right-aligned '
+                  'within the available  |\n'
+                  '   |           | space (this is the default for '
+                  'numbers).                   |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'=\'"     | Forces the padding to be placed after '
+                  'the sign (if any)    |\n'
+                  '   |           | but before the digits.  This is used for '
+                  'printing fields   |\n'
+                  '   |           | in the form ‘+000000120’. This alignment '
+                  'option is only    |\n'
+                  '   |           | valid for numeric types.  It becomes the '
+                  'default when ‘0’  |\n'
+                  '   |           | immediately precedes the field '
+                  'width.                      |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'^\'"     | Forces the field to be centered within '
+                  'the available       |\n'
+                  '   |           | '
+                  'space.                                                     '
+                  '|\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '\n'
+                  'Note that unless a minimum field width is defined, the '
+                  'field width\n'
+                  'will always be the same size as the data to fill it, so '
+                  'that the\n'
+                  'alignment option has no meaning in this case.\n'
+                  '\n'
+                  'The *sign* option is only valid for number types, and can '
+                  'be one of\n'
+                  'the following:\n'
+                  '\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | Option    | '
+                  'Meaning                                                    '
+                  '|\n'
+                  '   '
+                  '+===========+============================================================+\n'
+                  '   | "\'+\'"     | indicates that a sign should be used for '
+                  'both positive as  |\n'
+                  '   |           | well as negative '
+                  'numbers.                                  |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'-\'"     | indicates that a sign should be used '
+                  'only for negative     |\n'
+                  '   |           | numbers (this is the default '
+                  'behavior).                    |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | space     | indicates that a leading space should be '
+                  'used on positive  |\n'
+                  '   |           | numbers, and a minus sign on negative '
+                  'numbers.             |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '\n'
+                  'The "\'#\'" option causes the “alternate form” to be used '
+                  'for the\n'
+                  'conversion.  The alternate form is defined differently for '
+                  'different\n'
+                  'types.  This option is only valid for integer, float, '
+                  'complex and\n'
+                  'Decimal types. For integers, when binary, octal, or '
+                  'hexadecimal output\n'
+                  'is used, this option adds the prefix respective "\'0b\'", '
+                  '"\'0o\'", or\n'
+                  '"\'0x\'" to the output value. For floats, complex and '
+                  'Decimal the\n'
+                  'alternate form causes the result of the conversion to '
+                  'always contain a\n'
+                  'decimal-point character, even if no digits follow it. '
+                  'Normally, a\n'
+                  'decimal-point character appears in the result of these '
+                  'conversions\n'
+                  'only if a digit follows it. In addition, for "\'g\'" and '
+                  '"\'G\'"\n'
+                  'conversions, trailing zeros are not removed from the '
+                  'result.\n'
+                  '\n'
+                  'The "\',\'" option signals the use of a comma for a '
+                  'thousands separator.\n'
+                  'For a locale aware separator, use the "\'n\'" integer '
+                  'presentation type\n'
+                  'instead.\n'
+                  '\n'
+                  'Changed in version 3.1: Added the "\',\'" option (see also '
+                  '**PEP 378**).\n'
+                  '\n'
+                  'The "\'_\'" option signals the use of an underscore for a '
+                  'thousands\n'
+                  'separator for floating point presentation types and for '
+                  'integer\n'
+                  'presentation type "\'d\'".  For integer presentation types '
+                  '"\'b\'", "\'o\'",\n'
+                  '"\'x\'", and "\'X\'", underscores will be inserted every 4 '
+                  'digits.  For\n'
+                  'other presentation types, specifying this option is an '
+                  'error.\n'
+                  '\n'
+                  'Changed in version 3.6: Added the "\'_\'" option (see also '
+                  '**PEP 515**).\n'
+                  '\n'
+                  '*width* is a decimal integer defining the minimum field '
+                  'width.  If not\n'
+                  'specified, then the field width will be determined by the '
+                  'content.\n'
+                  '\n'
+                  'When no explicit alignment is given, preceding the *width* '
+                  'field by a\n'
+                  'zero ("\'0\'") character enables sign-aware zero-padding '
+                  'for numeric\n'
+                  'types.  This is equivalent to a *fill* character of "\'0\'" '
+                  'with an\n'
+                  '*alignment* type of "\'=\'".\n'
+                  '\n'
+                  'The *precision* is a decimal number indicating how many '
+                  'digits should\n'
+                  'be displayed after the decimal point for a floating point '
+                  'value\n'
+                  'formatted with "\'f\'" and "\'F\'", or before and after the '
+                  'decimal point\n'
+                  'for a floating point value formatted with "\'g\'" or '
+                  '"\'G\'".  For non-\n'
+                  'number types the field indicates the maximum field size - '
+                  'in other\n'
+                  'words, how many characters will be used from the field '
+                  'content. The\n'
+                  '*precision* is not allowed for integer values.\n'
+                  '\n'
+                  'Finally, the *type* determines how the data should be '
+                  'presented.\n'
+                  '\n'
+                  'The available string presentation types are:\n'
+                  '\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | Type      | '
+                  'Meaning                                                    '
+                  '|\n'
+                  '   '
+                  '+===========+============================================================+\n'
+                  '   | "\'s\'"     | String format. This is the default type '
+                  'for strings and    |\n'
+                  '   |           | may be '
+                  'omitted.                                            |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | None      | The same as '
+                  '"\'s\'".                                         |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '\n'
+                  'The available integer presentation types are:\n'
+                  '\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | Type      | '
+                  'Meaning                                                    '
+                  '|\n'
+                  '   '
+                  '+===========+============================================================+\n'
+                  '   | "\'b\'"     | Binary format. Outputs the number in '
+                  'base 2.               |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'c\'"     | Character. Converts the integer to the '
+                  'corresponding       |\n'
+                  '   |           | unicode character before '
+                  'printing.                         |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'d\'"     | Decimal Integer. Outputs the number in '
+                  'base 10.            |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'o\'"     | Octal format. Outputs the number in base '
+                  '8.                |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'x\'"     | Hex format. Outputs the number in base '
+                  '16, using lower-    |\n'
+                  '   |           | case letters for the digits above '
+                  '9.                       |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'X\'"     | Hex format. Outputs the number in base '
+                  '16, using upper-    |\n'
+                  '   |           | case letters for the digits above '
+                  '9.                       |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'n\'"     | Number. This is the same as "\'d\'", '
+                  'except that it uses the |\n'
+                  '   |           | current locale setting to insert the '
+                  'appropriate number    |\n'
+                  '   |           | separator '
+                  'characters.                                      |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | None      | The same as '
+                  '"\'d\'".                                         |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '\n'
+                  'In addition to the above presentation types, integers can '
+                  'be formatted\n'
+                  'with the floating point presentation types listed below '
+                  '(except "\'n\'"\n'
+                  'and "None"). When doing so, "float()" is used to convert '
+                  'the integer\n'
+                  'to a floating point number before formatting.\n'
+                  '\n'
+                  'The available presentation types for floating point and '
+                  'decimal values\n'
+                  'are:\n'
+                  '\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | Type      | '
+                  'Meaning                                                    '
+                  '|\n'
+                  '   '
+                  '+===========+============================================================+\n'
+                  '   | "\'e\'"     | Exponent notation. Prints the number in '
+                  'scientific         |\n'
+                  '   |           | notation using the letter ‘e’ to indicate '
+                  'the exponent.    |\n'
+                  '   |           | The default precision is '
+                  '"6".                              |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'E\'"     | Exponent notation. Same as "\'e\'" '
+                  'except it uses an upper   |\n'
+                  '   |           | case ‘E’ as the separator '
+                  'character.                       |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'f\'"     | Fixed-point notation. Displays the '
+                  'number as a fixed-point |\n'
+                  '   |           | number. The default precision is '
+                  '"6".                      |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'F\'"     | Fixed-point notation. Same as "\'f\'", '
+                  'but converts "nan" to |\n'
+                  '   |           | "NAN" and "inf" to '
+                  '"INF".                                  |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'g\'"     | General format.  For a given precision '
+                  '"p >= 1", this      |\n'
+                  '   |           | rounds the number to "p" significant '
+                  'digits and then       |\n'
+                  '   |           | formats the result in either fixed-point '
+                  'format or in      |\n'
+                  '   |           | scientific notation, depending on its '
+                  'magnitude.  The      |\n'
+                  '   |           | precise rules are as follows: suppose that '
+                  'the result      |\n'
+                  '   |           | formatted with presentation type "\'e\'" '
+                  'and precision "p-1" |\n'
+                  '   |           | would have exponent "exp".  Then if "-4 <= '
+                  'exp < p", the   |\n'
+                  '   |           | number is formatted with presentation type '
+                  '"\'f\'" and       |\n'
+                  '   |           | precision "p-1-exp".  Otherwise, the '
+                  'number is formatted   |\n'
+                  '   |           | with presentation type "\'e\'" and '
+                  'precision "p-1". In both  |\n'
+                  '   |           | cases insignificant trailing zeros are '
+                  'removed from the    |\n'
+                  '   |           | significand, and the decimal point is also '
+                  'removed if      |\n'
+                  '   |           | there are no remaining digits following '
+                  'it.  Positive and  |\n'
+                  '   |           | negative infinity, positive and negative '
+                  'zero, and nans,   |\n'
+                  '   |           | are formatted as "inf", "-inf", "0", "-0" '
+                  'and "nan"        |\n'
+                  '   |           | respectively, regardless of the '
+                  'precision.  A precision of |\n'
+                  '   |           | "0" is treated as equivalent to a '
+                  'precision of "1". The    |\n'
+                  '   |           | default precision is '
+                  '"6".                                  |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'G\'"     | General format. Same as "\'g\'" except '
+                  'switches to "\'E\'" if  |\n'
+                  '   |           | the number gets too large. The '
+                  'representations of infinity |\n'
+                  '   |           | and NaN are uppercased, '
+                  'too.                               |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'n\'"     | Number. This is the same as "\'g\'", '
+                  'except that it uses the |\n'
+                  '   |           | current locale setting to insert the '
+                  'appropriate number    |\n'
+                  '   |           | separator '
+                  'characters.                                      |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | "\'%\'"     | Percentage. Multiplies the number by 100 '
+                  'and displays in   |\n'
+                  '   |           | fixed ("\'f\'") format, followed by a '
+                  'percent sign.          |\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '   | None      | Similar to "\'g\'", except that '
+                  'fixed-point notation, when   |\n'
+                  '   |           | used, has at least one digit past the '
+                  'decimal point. The   |\n'
+                  '   |           | default precision is as high as needed to '
+                  'represent the    |\n'
+                  '   |           | particular value. The overall effect is to '
+                  'match the       |\n'
+                  '   |           | output of "str()" as altered by the other '
+                  'format           |\n'
+                  '   |           | '
+                  'modifiers.                                                 '
+                  '|\n'
+                  '   '
+                  '+-----------+------------------------------------------------------------+\n'
+                  '\n'
+                  '\n'
+                  'Format examples\n'
+                  '===============\n'
+                  '\n'
+                  'This section contains examples of the "str.format()" syntax '
+                  'and\n'
+                  'comparison with the old "%"-formatting.\n'
+                  '\n'
+                  'In most of the cases the syntax is similar to the old '
+                  '"%"-formatting,\n'
+                  'with the addition of the "{}" and with ":" used instead of '
+                  '"%". For\n'
+                  'example, "\'%03.2f\'" can be translated to "\'{:03.2f}\'".\n'
+                  '\n'
+                  'The new format syntax also supports new and different '
+                  'options, shown\n'
+                  'in the following examples.\n'
+                  '\n'
+                  'Accessing arguments by position:\n'
+                  '\n'
+                  "   >>> '{0}, {1}, {2}'.format('a', 'b', 'c')\n"
+                  "   'a, b, c'\n"
+                  "   >>> '{}, {}, {}'.format('a', 'b', 'c')  # 3.1+ only\n"
+                  "   'a, b, c'\n"
+                  "   >>> '{2}, {1}, {0}'.format('a', 'b', 'c')\n"
+                  "   'c, b, a'\n"
+                  "   >>> '{2}, {1}, {0}'.format(*'abc')      # unpacking "
+                  'argument sequence\n'
+                  "   'c, b, a'\n"
+                  "   >>> '{0}{1}{0}'.format('abra', 'cad')   # arguments' "
+                  'indices can be repeated\n'
+                  "   'abracadabra'\n"
+                  '\n'
+                  'Accessing arguments by name:\n'
+                  '\n'
+                  "   >>> 'Coordinates: {latitude}, "
+                  "{longitude}'.format(latitude='37.24N', "
+                  "longitude='-115.81W')\n"
+                  "   'Coordinates: 37.24N, -115.81W'\n"
+                  "   >>> coord = {'latitude': '37.24N', 'longitude': "
+                  "'-115.81W'}\n"
+                  "   >>> 'Coordinates: {latitude}, "
+                  "{longitude}'.format(**coord)\n"
+                  "   'Coordinates: 37.24N, -115.81W'\n"
+                  '\n'
+                  'Accessing arguments’ attributes:\n'
+                  '\n'
+                  '   >>> c = 3-5j\n'
+                  "   >>> ('The complex number {0} is formed from the real "
+                  "part {0.real} '\n"
+                  "   ...  'and the imaginary part {0.imag}.').format(c)\n"
+                  "   'The complex number (3-5j) is formed from the real part "
+                  "3.0 and the imaginary part -5.0.'\n"
+                  '   >>> class Point:\n'
+                  '   ...     def __init__(self, x, y):\n'
+                  '   ...         self.x, self.y = x, y\n'
+                  '   ...     def __str__(self):\n'
+                  "   ...         return 'Point({self.x}, "
+                  "{self.y})'.format(self=self)\n"
+                  '   ...\n'
+                  '   >>> str(Point(4, 2))\n'
+                  "   'Point(4, 2)'\n"
+                  '\n'
+                  'Accessing arguments’ items:\n'
+                  '\n'
+                  '   >>> coord = (3, 5)\n'
+                  "   >>> 'X: {0[0]};  Y: {0[1]}'.format(coord)\n"
+                  "   'X: 3;  Y: 5'\n"
+                  '\n'
+                  'Replacing "%s" and "%r":\n'
+                  '\n'
+                  '   >>> "repr() shows quotes: {!r}; str() doesn\'t: '
+                  '{!s}".format(\'test1\', \'test2\')\n'
+                  '   "repr() shows quotes: \'test1\'; str() doesn\'t: test2"\n'
+                  '\n'
+                  'Aligning the text and specifying a width:\n'
+                  '\n'
+                  "   >>> '{:<30}'.format('left aligned')\n"
+                  "   'left aligned                  '\n"
+                  "   >>> '{:>30}'.format('right aligned')\n"
+                  "   '                 right aligned'\n"
+                  "   >>> '{:^30}'.format('centered')\n"
+                  "   '           centered           '\n"
+                  "   >>> '{:*^30}'.format('centered')  # use '*' as a fill "
+                  'char\n'
+                  "   '***********centered***********'\n"
+                  '\n'
+                  'Replacing "%+f", "%-f", and "% f" and specifying a sign:\n'
+                  '\n'
+                  "   >>> '{:+f}; {:+f}'.format(3.14, -3.14)  # show it "
+                  'always\n'
+                  "   '+3.140000; -3.140000'\n"
+                  "   >>> '{: f}; {: f}'.format(3.14, -3.14)  # show a space "
+                  'for positive numbers\n'
+                  "   ' 3.140000; -3.140000'\n"
+                  "   >>> '{:-f}; {:-f}'.format(3.14, -3.14)  # show only the "
+                  "minus -- same as '{:f}; {:f}'\n"
+                  "   '3.140000; -3.140000'\n"
+                  '\n'
+                  'Replacing "%x" and "%o" and converting the value to '
+                  'different bases:\n'
+                  '\n'
+                  '   >>> # format also supports binary numbers\n'
+                  '   >>> "int: {0:d};  hex: {0:x};  oct: {0:o};  bin: '
+                  '{0:b}".format(42)\n'
+                  "   'int: 42;  hex: 2a;  oct: 52;  bin: 101010'\n"
+                  '   >>> # with 0x, 0o, or 0b as prefix:\n'
+                  '   >>> "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: '
+                  '{0:#b}".format(42)\n'
+                  "   'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'\n"
+                  '\n'
+                  'Using the comma as a thousands separator:\n'
+                  '\n'
+                  "   >>> '{:,}'.format(1234567890)\n"
+                  "   '1,234,567,890'\n"
+                  '\n'
+                  'Expressing a percentage:\n'
+                  '\n'
+                  '   >>> points = 19\n'
+                  '   >>> total = 22\n'
+                  "   >>> 'Correct answers: {:.2%}'.format(points/total)\n"
+                  "   'Correct answers: 86.36%'\n"
+                  '\n'
+                  'Using type-specific formatting:\n'
+                  '\n'
+                  '   >>> import datetime\n'
+                  '   >>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)\n'
+                  "   >>> '{:%Y-%m-%d %H:%M:%S}'.format(d)\n"
+                  "   '2010-07-04 12:15:58'\n"
+                  '\n'
+                  'Nesting arguments and more complex examples:\n'
+                  '\n'
+                  "   >>> for align, text in zip('<^>', ['left', 'center', "
+                  "'right']):\n"
+                  "   ...     '{0:{fill}{align}16}'.format(text, fill=align, "
+                  'align=align)\n'
+                  '   ...\n'
+                  "   'left<<<<<<<<<<<<'\n"
+                  "   '^^^^^center^^^^^'\n"
+                  "   '>>>>>>>>>>>right'\n"
+                  '   >>>\n'
+                  '   >>> octets = [192, 168, 0, 1]\n'
+                  "   >>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)\n"
+                  "   'C0A80001'\n"
+                  '   >>> int(_, 16)\n'
+                  '   3232235521\n'
+                  '   >>>\n'
+                  '   >>> width = 5\n'
+                  '   >>> for num in range(5,12): \n'
+                  "   ...     for base in 'dXob':\n"
+                  "   ...         print('{0:{width}{base}}'.format(num, "
+                  "base=base, width=width), end=' ')\n"
+                  '   ...     print()\n'
+                  '   ...\n'
+                  '       5     5     5   101\n'
+                  '       6     6     6   110\n'
+                  '       7     7     7   111\n'
+                  '       8     8    10  1000\n'
+                  '       9     9    11  1001\n'
+                  '      10     A    12  1010\n'
+                  '      11     B    13  1011\n',
+ 'function': 'Function definitions\n'
+             '********************\n'
+             '\n'
+             'A function definition defines a user-defined function object '
+             '(see\n'
+             'section The standard type hierarchy):\n'
+             '\n'
+             '   funcdef                 ::= [decorators] "def" funcname "(" '
+             '[parameter_list] ")"\n'
+             '               ["->" expression] ":" suite\n'
+             '   decorators              ::= decorator+\n'
+             '   decorator               ::= "@" dotted_name ["(" '
+             '[argument_list [","]] ")"] NEWLINE\n'
+             '   dotted_name             ::= identifier ("." identifier)*\n'
+             '   parameter_list          ::= defparameter ("," defparameter)* '
+             '["," [parameter_list_starargs]]\n'
+             '                      | parameter_list_starargs\n'
+             '   parameter_list_starargs ::= "*" [parameter] ("," '
+             'defparameter)* ["," ["**" parameter [","]]]\n'
+             '                               | "**" parameter [","]\n'
+             '   parameter               ::= identifier [":" expression]\n'
+             '   defparameter            ::= parameter ["=" expression]\n'
+             '   funcname                ::= identifier\n'
+             '\n'
+             'A function definition is an executable statement.  Its execution '
+             'binds\n'
+             'the function name in the current local namespace to a function '
+             'object\n'
+             '(a wrapper around the executable code for the function).  This\n'
+             'function object contains a reference to the current global '
+             'namespace\n'
+             'as the global namespace to be used when the function is called.\n'
+             '\n'
+             'The function definition does not execute the function body; this '
+             'gets\n'
+             'executed only when the function is called. [2]\n'
+             '\n'
+             'A function definition may be wrapped by one or more *decorator*\n'
+             'expressions. Decorator expressions are evaluated when the '
+             'function is\n'
+             'defined, in the scope that contains the function definition.  '
+             'The\n'
+             'result must be a callable, which is invoked with the function '
+             'object\n'
+             'as the only argument. The returned value is bound to the '
+             'function name\n'
+             'instead of the function object.  Multiple decorators are applied '
+             'in\n'
+             'nested fashion. For example, the following code\n'
+             '\n'
+             '   @f1(arg)\n'
+             '   @f2\n'
+             '   def func(): pass\n'
+             '\n'
+             'is roughly equivalent to\n'
+             '\n'
+             '   def func(): pass\n'
+             '   func = f1(arg)(f2(func))\n'
+             '\n'
+             'except that the original function is not temporarily bound to '
+             'the name\n'
+             '"func".\n'
+             '\n'
+             'When one or more *parameters* have the form *parameter* "="\n'
+             '*expression*, the function is said to have “default parameter '
+             'values.”\n'
+             'For a parameter with a default value, the corresponding '
+             '*argument* may\n'
+             'be omitted from a call, in which case the parameter’s default '
+             'value is\n'
+             'substituted.  If a parameter has a default value, all following\n'
+             'parameters up until the “"*"” must also have a default value — '
+             'this is\n'
+             'a syntactic restriction that is not expressed by the grammar.\n'
+             '\n'
+             '**Default parameter values are evaluated from left to right when '
+             'the\n'
+             'function definition is executed.** This means that the '
+             'expression is\n'
+             'evaluated once, when the function is defined, and that the same '
+             '“pre-\n'
+             'computed” value is used for each call.  This is especially '
+             'important\n'
+             'to understand when a default parameter is a mutable object, such '
+             'as a\n'
+             'list or a dictionary: if the function modifies the object (e.g. '
+             'by\n'
+             'appending an item to a list), the default value is in effect '
+             'modified.\n'
+             'This is generally not what was intended.  A way around this is '
+             'to use\n'
+             '"None" as the default, and explicitly test for it in the body of '
+             'the\n'
+             'function, e.g.:\n'
+             '\n'
+             '   def whats_on_the_telly(penguin=None):\n'
+             '       if penguin is None:\n'
+             '           penguin = []\n'
+             '       penguin.append("property of the zoo")\n'
+             '       return penguin\n'
+             '\n'
+             'Function call semantics are described in more detail in section '
+             'Calls.\n'
+             'A function call always assigns values to all parameters '
+             'mentioned in\n'
+             'the parameter list, either from position arguments, from '
+             'keyword\n'
+             'arguments, or from default values.  If the form “"*identifier"” '
+             'is\n'
+             'present, it is initialized to a tuple receiving any excess '
+             'positional\n'
+             'parameters, defaulting to the empty tuple. If the form\n'
+             '“"**identifier"” is present, it is initialized to a new ordered\n'
+             'mapping receiving any excess keyword arguments, defaulting to a '
+             'new\n'
+             'empty mapping of the same type.  Parameters after “"*"” or\n'
+             '“"*identifier"” are keyword-only parameters and may only be '
+             'passed\n'
+             'used keyword arguments.\n'
+             '\n'
+             'Parameters may have annotations of the form “": expression"” '
+             'following\n'
+             'the parameter name.  Any parameter may have an annotation even '
+             'those\n'
+             'of the form "*identifier" or "**identifier".  Functions may '
+             'have\n'
+             '“return” annotation of the form “"-> expression"” after the '
+             'parameter\n'
+             'list.  These annotations can be any valid Python expression and '
+             'are\n'
+             'evaluated when the function definition is executed.  Annotations '
+             'may\n'
+             'be evaluated in a different order than they appear in the source '
+             'code.\n'
+             'The presence of annotations does not change the semantics of a\n'
+             'function.  The annotation values are available as values of a\n'
+             'dictionary keyed by the parameters’ names in the '
+             '"__annotations__"\n'
+             'attribute of the function object.\n'
+             '\n'
+             'It is also possible to create anonymous functions (functions not '
+             'bound\n'
+             'to a name), for immediate use in expressions.  This uses lambda\n'
+             'expressions, described in section Lambdas.  Note that the '
+             'lambda\n'
+             'expression is merely a shorthand for a simplified function '
+             'definition;\n'
+             'a function defined in a “"def"” statement can be passed around '
+             'or\n'
+             'assigned to another name just like a function defined by a '
+             'lambda\n'
+             'expression.  The “"def"” form is actually more powerful since '
+             'it\n'
+             'allows the execution of multiple statements and annotations.\n'
+             '\n'
+             '**Programmer’s note:** Functions are first-class objects.  A '
+             '“"def"”\n'
+             'statement executed inside a function definition defines a local\n'
+             'function that can be returned or passed around.  Free variables '
+             'used\n'
+             'in the nested function can access the local variables of the '
+             'function\n'
+             'containing the def.  See section Naming and binding for '
+             'details.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 3107** - Function Annotations\n'
+             '     The original specification for function annotations.\n',
+ 'global': 'The "global" statement\n'
+           '**********************\n'
+           '\n'
+           '   global_stmt ::= "global" identifier ("," identifier)*\n'
+           '\n'
+           'The "global" statement is a declaration which holds for the '
+           'entire\n'
+           'current code block.  It means that the listed identifiers are to '
+           'be\n'
+           'interpreted as globals.  It would be impossible to assign to a '
+           'global\n'
+           'variable without "global", although free variables may refer to\n'
+           'globals without being declared global.\n'
+           '\n'
+           'Names listed in a "global" statement must not be used in the same '
+           'code\n'
+           'block textually preceding that "global" statement.\n'
+           '\n'
+           'Names listed in a "global" statement must not be defined as '
+           'formal\n'
+           'parameters or in a "for" loop control target, "class" definition,\n'
+           'function definition, "import" statement, or variable annotation.\n'
+           '\n'
+           '**CPython implementation detail:** The current implementation does '
+           'not\n'
+           'enforce some of these restrictions, but programs should not abuse '
+           'this\n'
+           'freedom, as future implementations may enforce them or silently '
+           'change\n'
+           'the meaning of the program.\n'
+           '\n'
+           '**Programmer’s note:** "global" is a directive to the parser.  It\n'
+           'applies only to code parsed at the same time as the "global"\n'
+           'statement. In particular, a "global" statement contained in a '
+           'string\n'
+           'or code object supplied to the built-in "exec()" function does '
+           'not\n'
+           'affect the code block *containing* the function call, and code\n'
+           'contained in such a string is unaffected by "global" statements in '
+           'the\n'
+           'code containing the function call.  The same applies to the '
+           '"eval()"\n'
+           'and "compile()" functions.\n',
+ 'id-classes': 'Reserved classes of identifiers\n'
+               '*******************************\n'
+               '\n'
+               'Certain classes of identifiers (besides keywords) have '
+               'special\n'
+               'meanings.  These classes are identified by the patterns of '
+               'leading and\n'
+               'trailing underscore characters:\n'
+               '\n'
+               '"_*"\n'
+               '   Not imported by "from module import *".  The special '
+               'identifier "_"\n'
+               '   is used in the interactive interpreter to store the result '
+               'of the\n'
+               '   last evaluation; it is stored in the "builtins" module.  '
+               'When not\n'
+               '   in interactive mode, "_" has no special meaning and is not '
+               'defined.\n'
+               '   See section The import statement.\n'
+               '\n'
+               '   Note: The name "_" is often used in conjunction with\n'
+               '     internationalization; refer to the documentation for the\n'
+               '     "gettext" module for more information on this '
+               'convention.\n'
+               '\n'
+               '"__*__"\n'
+               '   System-defined names. These names are defined by the '
+               'interpreter\n'
+               '   and its implementation (including the standard library).  '
+               'Current\n'
+               '   system names are discussed in the Special method names '
+               'section and\n'
+               '   elsewhere.  More will likely be defined in future versions '
+               'of\n'
+               '   Python.  *Any* use of "__*__" names, in any context, that '
+               'does not\n'
+               '   follow explicitly documented use, is subject to breakage '
+               'without\n'
+               '   warning.\n'
+               '\n'
+               '"__*"\n'
+               '   Class-private names.  Names in this category, when used '
+               'within the\n'
+               '   context of a class definition, are re-written to use a '
+               'mangled form\n'
+               '   to help avoid name clashes between “private” attributes of '
+               'base and\n'
+               '   derived classes. See section Identifiers (Names).\n',
+ 'identifiers': 'Identifiers and keywords\n'
+                '************************\n'
+                '\n'
+                'Identifiers (also referred to as *names*) are described by '
+                'the\n'
+                'following lexical definitions.\n'
+                '\n'
+                'The syntax of identifiers in Python is based on the Unicode '
+                'standard\n'
+                'annex UAX-31, with elaboration and changes as defined below; '
+                'see also\n'
+                '**PEP 3131** for further details.\n'
+                '\n'
+                'Within the ASCII range (U+0001..U+007F), the valid characters '
+                'for\n'
+                'identifiers are the same as in Python 2.x: the uppercase and '
+                'lowercase\n'
+                'letters "A" through "Z", the underscore "_" and, except for '
+                'the first\n'
+                'character, the digits "0" through "9".\n'
+                '\n'
+                'Python 3.0 introduces additional characters from outside the '
+                'ASCII\n'
+                'range (see **PEP 3131**).  For these characters, the '
+                'classification\n'
+                'uses the version of the Unicode Character Database as '
+                'included in the\n'
+                '"unicodedata" module.\n'
+                '\n'
+                'Identifiers are unlimited in length.  Case is significant.\n'
+                '\n'
+                '   identifier   ::= xid_start xid_continue*\n'
+                '   id_start     ::= <all characters in general categories Lu, '
+                'Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the '
+                'Other_ID_Start property>\n'
+                '   id_continue  ::= <all characters in id_start, plus '
+                'characters in the categories Mn, Mc, Nd, Pc and others with '
+                'the Other_ID_Continue property>\n'
+                '   xid_start    ::= <all characters in id_start whose NFKC '
+                'normalization is in "id_start xid_continue*">\n'
+                '   xid_continue ::= <all characters in id_continue whose NFKC '
+                'normalization is in "id_continue*">\n'
+                '\n'
+                'The Unicode category codes mentioned above stand for:\n'
+                '\n'
+                '* *Lu* - uppercase letters\n'
+                '\n'
+                '* *Ll* - lowercase letters\n'
+                '\n'
+                '* *Lt* - titlecase letters\n'
+                '\n'
+                '* *Lm* - modifier letters\n'
+                '\n'
+                '* *Lo* - other letters\n'
+                '\n'
+                '* *Nl* - letter numbers\n'
+                '\n'
+                '* *Mn* - nonspacing marks\n'
+                '\n'
+                '* *Mc* - spacing combining marks\n'
+                '\n'
+                '* *Nd* - decimal numbers\n'
+                '\n'
+                '* *Pc* - connector punctuations\n'
+                '\n'
+                '* *Other_ID_Start* - explicit list of characters in '
+                'PropList.txt to\n'
+                '  support backwards compatibility\n'
+                '\n'
+                '* *Other_ID_Continue* - likewise\n'
+                '\n'
+                'All identifiers are converted into the normal form NFKC while '
+                'parsing;\n'
+                'comparison of identifiers is based on NFKC.\n'
+                '\n'
+                'A non-normative HTML file listing all valid identifier '
+                'characters for\n'
+                'Unicode 4.1 can be found at https://www.dcl.hpi.uni-\n'
+                'potsdam.de/home/loewis/table-3131.html.\n'
+                '\n'
+                '\n'
+                'Keywords\n'
+                '========\n'
+                '\n'
+                'The following identifiers are used as reserved words, or '
+                '*keywords* of\n'
+                'the language, and cannot be used as ordinary identifiers.  '
+                'They must\n'
+                'be spelled exactly as written here:\n'
+                '\n'
+                '   False      class      finally    is         return\n'
+                '   None       continue   for        lambda     try\n'
+                '   True       def        from       nonlocal   while\n'
+                '   and        del        global     not        with\n'
+                '   as         elif       if         or         yield\n'
+                '   assert     else       import     pass\n'
+                '   break      except     in         raise\n'
+                '\n'
+                '\n'
+                'Reserved classes of identifiers\n'
+                '===============================\n'
+                '\n'
+                'Certain classes of identifiers (besides keywords) have '
+                'special\n'
+                'meanings.  These classes are identified by the patterns of '
+                'leading and\n'
+                'trailing underscore characters:\n'
+                '\n'
+                '"_*"\n'
+                '   Not imported by "from module import *".  The special '
+                'identifier "_"\n'
+                '   is used in the interactive interpreter to store the result '
+                'of the\n'
+                '   last evaluation; it is stored in the "builtins" module.  '
+                'When not\n'
+                '   in interactive mode, "_" has no special meaning and is not '
+                'defined.\n'
+                '   See section The import statement.\n'
+                '\n'
+                '   Note: The name "_" is often used in conjunction with\n'
+                '     internationalization; refer to the documentation for '
+                'the\n'
+                '     "gettext" module for more information on this '
+                'convention.\n'
+                '\n'
+                '"__*__"\n'
+                '   System-defined names. These names are defined by the '
+                'interpreter\n'
+                '   and its implementation (including the standard library).  '
+                'Current\n'
+                '   system names are discussed in the Special method names '
+                'section and\n'
+                '   elsewhere.  More will likely be defined in future versions '
+                'of\n'
+                '   Python.  *Any* use of "__*__" names, in any context, that '
+                'does not\n'
+                '   follow explicitly documented use, is subject to breakage '
+                'without\n'
+                '   warning.\n'
+                '\n'
+                '"__*"\n'
+                '   Class-private names.  Names in this category, when used '
+                'within the\n'
+                '   context of a class definition, are re-written to use a '
+                'mangled form\n'
+                '   to help avoid name clashes between “private” attributes of '
+                'base and\n'
+                '   derived classes. See section Identifiers (Names).\n',
+ 'if': 'The "if" statement\n'
+       '******************\n'
+       '\n'
+       'The "if" statement is used for conditional execution:\n'
+       '\n'
+       '   if_stmt ::= "if" expression ":" suite\n'
+       '               ("elif" expression ":" suite)*\n'
+       '               ["else" ":" suite]\n'
+       '\n'
+       'It selects exactly one of the suites by evaluating the expressions '
+       'one\n'
+       'by one until one is found to be true (see section Boolean operations\n'
+       'for the definition of true and false); then that suite is executed\n'
+       '(and no other part of the "if" statement is executed or evaluated).\n'
+       'If all expressions are false, the suite of the "else" clause, if\n'
+       'present, is executed.\n',
+ 'imaginary': 'Imaginary literals\n'
+              '******************\n'
+              '\n'
+              'Imaginary literals are described by the following lexical '
+              'definitions:\n'
+              '\n'
+              '   imagnumber ::= (floatnumber | digitpart) ("j" | "J")\n'
+              '\n'
+              'An imaginary literal yields a complex number with a real part '
+              'of 0.0.\n'
+              'Complex numbers are represented as a pair of floating point '
+              'numbers\n'
+              'and have the same restrictions on their range.  To create a '
+              'complex\n'
+              'number with a nonzero real part, add a floating point number to '
+              'it,\n'
+              'e.g., "(3+4j)".  Some examples of imaginary literals:\n'
+              '\n'
+              '   3.14j   10.j    10j     .001j   1e100j   3.14e-10j   '
+              '3.14_15_93j\n',
+ 'import': 'The "import" statement\n'
+           '**********************\n'
+           '\n'
+           '   import_stmt     ::= "import" module ["as" identifier] ("," '
+           'module ["as" identifier])*\n'
+           '                   | "from" relative_module "import" identifier '
+           '["as" identifier]\n'
+           '                   ("," identifier ["as" identifier])*\n'
+           '                   | "from" relative_module "import" "(" '
+           'identifier ["as" identifier]\n'
+           '                   ("," identifier ["as" identifier])* [","] ")"\n'
+           '                   | "from" module "import" "*"\n'
+           '   module          ::= (identifier ".")* identifier\n'
+           '   relative_module ::= "."* module | "."+\n'
+           '\n'
+           'The basic import statement (no "from" clause) is executed in two\n'
+           'steps:\n'
+           '\n'
+           '1. find a module, loading and initializing it if necessary\n'
+           '\n'
+           '2. define a name or names in the local namespace for the scope\n'
+           '   where the "import" statement occurs.\n'
+           '\n'
+           'When the statement contains multiple clauses (separated by commas) '
+           'the\n'
+           'two steps are carried out separately for each clause, just as '
+           'though\n'
+           'the clauses had been separated out into individual import '
+           'statements.\n'
+           '\n'
+           'The details of the first step, finding and loading modules are\n'
+           'described in greater detail in the section on the import system, '
+           'which\n'
+           'also describes the various types of packages and modules that can '
+           'be\n'
+           'imported, as well as all the hooks that can be used to customize '
+           'the\n'
+           'import system. Note that failures in this step may indicate '
+           'either\n'
+           'that the module could not be located, *or* that an error occurred\n'
+           'while initializing the module, which includes execution of the\n'
+           'module’s code.\n'
+           '\n'
+           'If the requested module is retrieved successfully, it will be '
+           'made\n'
+           'available in the local namespace in one of three ways:\n'
+           '\n'
+           '* If the module name is followed by "as", then the name following\n'
+           '  "as" is bound directly to the imported module.\n'
+           '\n'
+           '* If no other name is specified, and the module being imported is '
+           'a\n'
+           '  top level module, the module’s name is bound in the local '
+           'namespace\n'
+           '  as a reference to the imported module\n'
+           '\n'
+           '* If the module being imported is *not* a top level module, then '
+           'the\n'
+           '  name of the top level package that contains the module is bound '
+           'in\n'
+           '  the local namespace as a reference to the top level package. '
+           'The\n'
+           '  imported module must be accessed using its full qualified name\n'
+           '  rather than directly\n'
+           '\n'
+           'The "from" form uses a slightly more complex process:\n'
+           '\n'
+           '1. find the module specified in the "from" clause, loading and\n'
+           '   initializing it if necessary;\n'
+           '\n'
+           '2. for each of the identifiers specified in the "import" clauses:\n'
+           '\n'
+           '   1. check if the imported module has an attribute by that name\n'
+           '\n'
+           '   2. if not, attempt to import a submodule with that name and '
+           'then\n'
+           '      check the imported module again for that attribute\n'
+           '\n'
+           '   3. if the attribute is not found, "ImportError" is raised.\n'
+           '\n'
+           '   4. otherwise, a reference to that value is stored in the local\n'
+           '      namespace, using the name in the "as" clause if it is '
+           'present,\n'
+           '      otherwise using the attribute name\n'
+           '\n'
+           'Examples:\n'
+           '\n'
+           '   import foo                 # foo imported and bound locally\n'
+           '   import foo.bar.baz         # foo.bar.baz imported, foo bound '
+           'locally\n'
+           '   import foo.bar.baz as fbb  # foo.bar.baz imported and bound as '
+           'fbb\n'
+           '   from foo.bar import baz    # foo.bar.baz imported and bound as '
+           'baz\n'
+           '   from foo import attr       # foo imported and foo.attr bound as '
+           'attr\n'
+           '\n'
+           'If the list of identifiers is replaced by a star ("\'*\'"), all '
+           'public\n'
+           'names defined in the module are bound in the local namespace for '
+           'the\n'
+           'scope where the "import" statement occurs.\n'
+           '\n'
+           'The *public names* defined by a module are determined by checking '
+           'the\n'
+           'module’s namespace for a variable named "__all__"; if defined, it '
+           'must\n'
+           'be a sequence of strings which are names defined or imported by '
+           'that\n'
+           'module.  The names given in "__all__" are all considered public '
+           'and\n'
+           'are required to exist.  If "__all__" is not defined, the set of '
+           'public\n'
+           'names includes all names found in the module’s namespace which do '
+           'not\n'
+           'begin with an underscore character ("\'_\'").  "__all__" should '
+           'contain\n'
+           'the entire public API. It is intended to avoid accidentally '
+           'exporting\n'
+           'items that are not part of the API (such as library modules which '
+           'were\n'
+           'imported and used within the module).\n'
+           '\n'
+           'The wild card form of import — "from module import *" — is only\n'
+           'allowed at the module level.  Attempting to use it in class or\n'
+           'function definitions will raise a "SyntaxError".\n'
+           '\n'
+           'When specifying what module to import you do not have to specify '
+           'the\n'
+           'absolute name of the module. When a module or package is '
+           'contained\n'
+           'within another package it is possible to make a relative import '
+           'within\n'
+           'the same top package without having to mention the package name. '
+           'By\n'
+           'using leading dots in the specified module or package after "from" '
+           'you\n'
+           'can specify how high to traverse up the current package hierarchy\n'
+           'without specifying exact names. One leading dot means the current\n'
+           'package where the module making the import exists. Two dots means '
+           'up\n'
+           'one package level. Three dots is up two levels, etc. So if you '
+           'execute\n'
+           '"from . import mod" from a module in the "pkg" package then you '
+           'will\n'
+           'end up importing "pkg.mod". If you execute "from ..subpkg2 import '
+           'mod"\n'
+           'from within "pkg.subpkg1" you will import "pkg.subpkg2.mod". The\n'
+           'specification for relative imports is contained within **PEP '
+           '328**.\n'
+           '\n'
+           '"importlib.import_module()" is provided to support applications '
+           'that\n'
+           'determine dynamically the modules to be loaded.\n'
+           '\n'
+           '\n'
+           'Future statements\n'
+           '=================\n'
+           '\n'
+           'A *future statement* is a directive to the compiler that a '
+           'particular\n'
+           'module should be compiled using syntax or semantics that will be\n'
+           'available in a specified future release of Python where the '
+           'feature\n'
+           'becomes standard.\n'
+           '\n'
+           'The future statement is intended to ease migration to future '
+           'versions\n'
+           'of Python that introduce incompatible changes to the language.  '
+           'It\n'
+           'allows use of the new features on a per-module basis before the\n'
+           'release in which the feature becomes standard.\n'
+           '\n'
+           '   future_stmt ::= "from" "__future__" "import" feature ["as" '
+           'identifier]\n'
+           '                   ("," feature ["as" identifier])*\n'
+           '                   | "from" "__future__" "import" "(" feature '
+           '["as" identifier]\n'
+           '                   ("," feature ["as" identifier])* [","] ")"\n'
+           '   feature     ::= identifier\n'
+           '\n'
+           'A future statement must appear near the top of the module.  The '
+           'only\n'
+           'lines that can appear before a future statement are:\n'
+           '\n'
+           '* the module docstring (if any),\n'
+           '\n'
+           '* comments,\n'
+           '\n'
+           '* blank lines, and\n'
+           '\n'
+           '* other future statements.\n'
+           '\n'
+           'The features recognized by Python 3.0 are "absolute_import",\n'
+           '"division", "generators", "unicode_literals", "print_function",\n'
+           '"nested_scopes" and "with_statement".  They are all redundant '
+           'because\n'
+           'they are always enabled, and only kept for backwards '
+           'compatibility.\n'
+           '\n'
+           'A future statement is recognized and treated specially at compile\n'
+           'time: Changes to the semantics of core constructs are often\n'
+           'implemented by generating different code.  It may even be the '
+           'case\n'
+           'that a new feature introduces new incompatible syntax (such as a '
+           'new\n'
+           'reserved word), in which case the compiler may need to parse the\n'
+           'module differently.  Such decisions cannot be pushed off until\n'
+           'runtime.\n'
+           '\n'
+           'For any given release, the compiler knows which feature names '
+           'have\n'
+           'been defined, and raises a compile-time error if a future '
+           'statement\n'
+           'contains a feature not known to it.\n'
+           '\n'
+           'The direct runtime semantics are the same as for any import '
+           'statement:\n'
+           'there is a standard module "__future__", described later, and it '
+           'will\n'
+           'be imported in the usual way at the time the future statement is\n'
+           'executed.\n'
+           '\n'
+           'The interesting runtime semantics depend on the specific feature\n'
+           'enabled by the future statement.\n'
+           '\n'
+           'Note that there is nothing special about the statement:\n'
+           '\n'
+           '   import __future__ [as name]\n'
+           '\n'
+           'That is not a future statement; it’s an ordinary import statement '
+           'with\n'
+           'no special semantics or syntax restrictions.\n'
+           '\n'
+           'Code compiled by calls to the built-in functions "exec()" and\n'
+           '"compile()" that occur in a module "M" containing a future '
+           'statement\n'
+           'will, by default, use the new syntax or semantics associated with '
+           'the\n'
+           'future statement.  This can be controlled by optional arguments '
+           'to\n'
+           '"compile()" — see the documentation of that function for details.\n'
+           '\n'
+           'A future statement typed at an interactive interpreter prompt '
+           'will\n'
+           'take effect for the rest of the interpreter session.  If an\n'
+           'interpreter is started with the "-i" option, is passed a script '
+           'name\n'
+           'to execute, and the script includes a future statement, it will be '
+           'in\n'
+           'effect in the interactive session started after the script is\n'
+           'executed.\n'
+           '\n'
+           'See also:\n'
+           '\n'
+           '  **PEP 236** - Back to the __future__\n'
+           '     The original proposal for the __future__ mechanism.\n',
+ 'in': 'Membership test operations\n'
+       '**************************\n'
+       '\n'
+       'The operators "in" and "not in" test for membership.  "x in s"\n'
+       'evaluates to "True" if *x* is a member of *s*, and "False" otherwise.\n'
+       '"x not in s" returns the negation of "x in s".  All built-in '
+       'sequences\n'
+       'and set types support this as well as dictionary, for which "in" '
+       'tests\n'
+       'whether the dictionary has a given key. For container types such as\n'
+       'list, tuple, set, frozenset, dict, or collections.deque, the\n'
+       'expression "x in y" is equivalent to "any(x is e or x == e for e in\n'
+       'y)".\n'
+       '\n'
+       'For the string and bytes types, "x in y" is "True" if and only if *x*\n'
+       'is a substring of *y*.  An equivalent test is "y.find(x) != -1".\n'
+       'Empty strings are always considered to be a substring of any other\n'
+       'string, so """ in "abc"" will return "True".\n'
+       '\n'
+       'For user-defined classes which define the "__contains__()" method, "x\n'
+       'in y" returns "True" if "y.__contains__(x)" returns a true value, and\n'
+       '"False" otherwise.\n'
+       '\n'
+       'For user-defined classes which do not define "__contains__()" but do\n'
+       'define "__iter__()", "x in y" is "True" if some value "z" with "x ==\n'
+       'z" is produced while iterating over "y".  If an exception is raised\n'
+       'during the iteration, it is as if "in" raised that exception.\n'
+       '\n'
+       'Lastly, the old-style iteration protocol is tried: if a class defines\n'
+       '"__getitem__()", "x in y" is "True" if and only if there is a non-\n'
+       'negative integer index *i* such that "x == y[i]", and all lower\n'
+       'integer indices do not raise "IndexError" exception.  (If any other\n'
+       'exception is raised, it is as if "in" raised that exception).\n'
+       '\n'
+       'The operator "not in" is defined to have the inverse true value of\n'
+       '"in".\n',
+ 'integers': 'Integer literals\n'
+             '****************\n'
+             '\n'
+             'Integer literals are described by the following lexical '
+             'definitions:\n'
+             '\n'
+             '   integer      ::= decinteger | bininteger | octinteger | '
+             'hexinteger\n'
+             '   decinteger   ::= nonzerodigit (["_"] digit)* | "0"+ (["_"] '
+             '"0")*\n'
+             '   bininteger   ::= "0" ("b" | "B") (["_"] bindigit)+\n'
+             '   octinteger   ::= "0" ("o" | "O") (["_"] octdigit)+\n'
+             '   hexinteger   ::= "0" ("x" | "X") (["_"] hexdigit)+\n'
+             '   nonzerodigit ::= "1"..."9"\n'
+             '   digit        ::= "0"..."9"\n'
+             '   bindigit     ::= "0" | "1"\n'
+             '   octdigit     ::= "0"..."7"\n'
+             '   hexdigit     ::= digit | "a"..."f" | "A"..."F"\n'
+             '\n'
+             'There is no limit for the length of integer literals apart from '
+             'what\n'
+             'can be stored in available memory.\n'
+             '\n'
+             'Underscores are ignored for determining the numeric value of '
+             'the\n'
+             'literal.  They can be used to group digits for enhanced '
+             'readability.\n'
+             'One underscore can occur between digits, and after base '
+             'specifiers\n'
+             'like "0x".\n'
+             '\n'
+             'Note that leading zeros in a non-zero decimal number are not '
+             'allowed.\n'
+             'This is for disambiguation with C-style octal literals, which '
+             'Python\n'
+             'used before version 3.0.\n'
+             '\n'
+             'Some examples of integer literals:\n'
+             '\n'
+             '   7     2147483647                        0o177    0b100110111\n'
+             '   3     79228162514264337593543950336     0o377    0xdeadbeef\n'
+             '         100_000_000_000                   0b_1110_0101\n'
+             '\n'
+             'Changed in version 3.6: Underscores are now allowed for '
+             'grouping\n'
+             'purposes in literals.\n',
+ 'lambda': 'Lambdas\n'
+           '*******\n'
+           '\n'
+           '   lambda_expr        ::= "lambda" [parameter_list] ":" '
+           'expression\n'
+           '   lambda_expr_nocond ::= "lambda" [parameter_list] ":" '
+           'expression_nocond\n'
+           '\n'
+           'Lambda expressions (sometimes called lambda forms) are used to '
+           'create\n'
+           'anonymous functions. The expression "lambda parameters: '
+           'expression"\n'
+           'yields a function object.  The unnamed object behaves like a '
+           'function\n'
+           'object defined with:\n'
+           '\n'
+           '   def <lambda>(parameters):\n'
+           '       return expression\n'
+           '\n'
+           'See section Function definitions for the syntax of parameter '
+           'lists.\n'
+           'Note that functions created with lambda expressions cannot '
+           'contain\n'
+           'statements or annotations.\n',
+ 'lists': 'List displays\n'
+          '*************\n'
+          '\n'
+          'A list display is a possibly empty series of expressions enclosed '
+          'in\n'
+          'square brackets:\n'
+          '\n'
+          '   list_display ::= "[" [starred_list | comprehension] "]"\n'
+          '\n'
+          'A list display yields a new list object, the contents being '
+          'specified\n'
+          'by either a list of expressions or a comprehension.  When a comma-\n'
+          'separated list of expressions is supplied, its elements are '
+          'evaluated\n'
+          'from left to right and placed into the list object in that order.\n'
+          'When a comprehension is supplied, the list is constructed from the\n'
+          'elements resulting from the comprehension.\n',
+ 'naming': 'Naming and binding\n'
+           '******************\n'
+           '\n'
+           '\n'
+           'Binding of names\n'
+           '================\n'
+           '\n'
+           '*Names* refer to objects.  Names are introduced by name binding\n'
+           'operations.\n'
+           '\n'
+           'The following constructs bind names: formal parameters to '
+           'functions,\n'
+           '"import" statements, class and function definitions (these bind '
+           'the\n'
+           'class or function name in the defining block), and targets that '
+           'are\n'
+           'identifiers if occurring in an assignment, "for" loop header, or '
+           'after\n'
+           '"as" in a "with" statement or "except" clause. The "import" '
+           'statement\n'
+           'of the form "from ... import *" binds all names defined in the\n'
+           'imported module, except those beginning with an underscore.  This '
+           'form\n'
+           'may only be used at the module level.\n'
+           '\n'
+           'A target occurring in a "del" statement is also considered bound '
+           'for\n'
+           'this purpose (though the actual semantics are to unbind the '
+           'name).\n'
+           '\n'
+           'Each assignment or import statement occurs within a block defined '
+           'by a\n'
+           'class or function definition or at the module level (the '
+           'top-level\n'
+           'code block).\n'
+           '\n'
+           'If a name is bound in a block, it is a local variable of that '
+           'block,\n'
+           'unless declared as "nonlocal" or "global".  If a name is bound at '
+           'the\n'
+           'module level, it is a global variable.  (The variables of the '
+           'module\n'
+           'code block are local and global.)  If a variable is used in a '
+           'code\n'
+           'block but not defined there, it is a *free variable*.\n'
+           '\n'
+           'Each occurrence of a name in the program text refers to the '
+           '*binding*\n'
+           'of that name established by the following name resolution rules.\n'
+           '\n'
+           '\n'
+           'Resolution of names\n'
+           '===================\n'
+           '\n'
+           'A *scope* defines the visibility of a name within a block.  If a '
+           'local\n'
+           'variable is defined in a block, its scope includes that block.  If '
+           'the\n'
+           'definition occurs in a function block, the scope extends to any '
+           'blocks\n'
+           'contained within the defining one, unless a contained block '
+           'introduces\n'
+           'a different binding for the name.\n'
+           '\n'
+           'When a name is used in a code block, it is resolved using the '
+           'nearest\n'
+           'enclosing scope.  The set of all such scopes visible to a code '
+           'block\n'
+           'is called the block’s *environment*.\n'
+           '\n'
+           'When a name is not found at all, a "NameError" exception is '
+           'raised. If\n'
+           'the current scope is a function scope, and the name refers to a '
+           'local\n'
+           'variable that has not yet been bound to a value at the point where '
+           'the\n'
+           'name is used, an "UnboundLocalError" exception is raised.\n'
+           '"UnboundLocalError" is a subclass of "NameError".\n'
+           '\n'
+           'If a name binding operation occurs anywhere within a code block, '
+           'all\n'
+           'uses of the name within the block are treated as references to '
+           'the\n'
+           'current block.  This can lead to errors when a name is used within '
+           'a\n'
+           'block before it is bound.  This rule is subtle.  Python lacks\n'
+           'declarations and allows name binding operations to occur anywhere\n'
+           'within a code block.  The local variables of a code block can be\n'
+           'determined by scanning the entire text of the block for name '
+           'binding\n'
+           'operations.\n'
+           '\n'
+           'If the "global" statement occurs within a block, all uses of the '
+           'name\n'
+           'specified in the statement refer to the binding of that name in '
+           'the\n'
+           'top-level namespace.  Names are resolved in the top-level '
+           'namespace by\n'
+           'searching the global namespace, i.e. the namespace of the module\n'
+           'containing the code block, and the builtins namespace, the '
+           'namespace\n'
+           'of the module "builtins".  The global namespace is searched '
+           'first.  If\n'
+           'the name is not found there, the builtins namespace is searched.  '
+           'The\n'
+           '"global" statement must precede all uses of the name.\n'
+           '\n'
+           'The "global" statement has the same scope as a name binding '
+           'operation\n'
+           'in the same block.  If the nearest enclosing scope for a free '
+           'variable\n'
+           'contains a global statement, the free variable is treated as a '
+           'global.\n'
+           '\n'
+           'The "nonlocal" statement causes corresponding names to refer to\n'
+           'previously bound variables in the nearest enclosing function '
+           'scope.\n'
+           '"SyntaxError" is raised at compile time if the given name does '
+           'not\n'
+           'exist in any enclosing function scope.\n'
+           '\n'
+           'The namespace for a module is automatically created the first time '
+           'a\n'
+           'module is imported.  The main module for a script is always '
+           'called\n'
+           '"__main__".\n'
+           '\n'
+           'Class definition blocks and arguments to "exec()" and "eval()" '
+           'are\n'
+           'special in the context of name resolution. A class definition is '
+           'an\n'
+           'executable statement that may use and define names. These '
+           'references\n'
+           'follow the normal rules for name resolution with an exception '
+           'that\n'
+           'unbound local variables are looked up in the global namespace. '
+           'The\n'
+           'namespace of the class definition becomes the attribute dictionary '
+           'of\n'
+           'the class. The scope of names defined in a class block is limited '
+           'to\n'
+           'the class block; it does not extend to the code blocks of methods '
+           '–\n'
+           'this includes comprehensions and generator expressions since they '
+           'are\n'
+           'implemented using a function scope.  This means that the '
+           'following\n'
+           'will fail:\n'
+           '\n'
+           '   class A:\n'
+           '       a = 42\n'
+           '       b = list(a + i for i in range(10))\n'
+           '\n'
+           '\n'
+           'Builtins and restricted execution\n'
+           '=================================\n'
+           '\n'
+           '**CPython implementation detail:** Users should not touch\n'
+           '"__builtins__"; it is strictly an implementation detail.  Users\n'
+           'wanting to override values in the builtins namespace should '
+           '"import"\n'
+           'the "builtins" module and modify its attributes appropriately.\n'
+           '\n'
+           'The builtins namespace associated with the execution of a code '
+           'block\n'
+           'is actually found by looking up the name "__builtins__" in its '
+           'global\n'
+           'namespace; this should be a dictionary or a module (in the latter '
+           'case\n'
+           'the module’s dictionary is used).  By default, when in the '
+           '"__main__"\n'
+           'module, "__builtins__" is the built-in module "builtins"; when in '
+           'any\n'
+           'other module, "__builtins__" is an alias for the dictionary of '
+           'the\n'
+           '"builtins" module itself.\n'
+           '\n'
+           '\n'
+           'Interaction with dynamic features\n'
+           '=================================\n'
+           '\n'
+           'Name resolution of free variables occurs at runtime, not at '
+           'compile\n'
+           'time. This means that the following code will print 42:\n'
+           '\n'
+           '   i = 10\n'
+           '   def f():\n'
+           '       print(i)\n'
+           '   i = 42\n'
+           '   f()\n'
+           '\n'
+           'The "eval()" and "exec()" functions do not have access to the '
+           'full\n'
+           'environment for resolving names.  Names may be resolved in the '
+           'local\n'
+           'and global namespaces of the caller.  Free variables are not '
+           'resolved\n'
+           'in the nearest enclosing namespace, but in the global namespace.  '
+           '[1]\n'
+           'The "exec()" and "eval()" functions have optional arguments to\n'
+           'override the global and local namespace.  If only one namespace '
+           'is\n'
+           'specified, it is used for both.\n',
+ 'nonlocal': 'The "nonlocal" statement\n'
+             '************************\n'
+             '\n'
+             '   nonlocal_stmt ::= "nonlocal" identifier ("," identifier)*\n'
+             '\n'
+             'The "nonlocal" statement causes the listed identifiers to refer '
+             'to\n'
+             'previously bound variables in the nearest enclosing scope '
+             'excluding\n'
+             'globals. This is important because the default behavior for '
+             'binding is\n'
+             'to search the local namespace first.  The statement allows\n'
+             'encapsulated code to rebind variables outside of the local '
+             'scope\n'
+             'besides the global (module) scope.\n'
+             '\n'
+             'Names listed in a "nonlocal" statement, unlike those listed in '
+             'a\n'
+             '"global" statement, must refer to pre-existing bindings in an\n'
+             'enclosing scope (the scope in which a new binding should be '
+             'created\n'
+             'cannot be determined unambiguously).\n'
+             '\n'
+             'Names listed in a "nonlocal" statement must not collide with '
+             'pre-\n'
+             'existing bindings in the local scope.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  **PEP 3104** - Access to Names in Outer Scopes\n'
+             '     The specification for the "nonlocal" statement.\n',
+ 'numbers': 'Numeric literals\n'
+            '****************\n'
+            '\n'
+            'There are three types of numeric literals: integers, floating '
+            'point\n'
+            'numbers, and imaginary numbers.  There are no complex literals\n'
+            '(complex numbers can be formed by adding a real number and an\n'
+            'imaginary number).\n'
+            '\n'
+            'Note that numeric literals do not include a sign; a phrase like '
+            '"-1"\n'
+            'is actually an expression composed of the unary operator ‘"-"‘ '
+            'and the\n'
+            'literal "1".\n',
+ 'numeric-types': 'Emulating numeric types\n'
+                  '***********************\n'
+                  '\n'
+                  'The following methods can be defined to emulate numeric '
+                  'objects.\n'
+                  'Methods corresponding to operations that are not supported '
+                  'by the\n'
+                  'particular kind of number implemented (e.g., bitwise '
+                  'operations for\n'
+                  'non-integral numbers) should be left undefined.\n'
+                  '\n'
+                  'object.__add__(self, other)\n'
+                  'object.__sub__(self, other)\n'
+                  'object.__mul__(self, other)\n'
+                  'object.__matmul__(self, other)\n'
+                  'object.__truediv__(self, other)\n'
+                  'object.__floordiv__(self, other)\n'
+                  'object.__mod__(self, other)\n'
+                  'object.__divmod__(self, other)\n'
+                  'object.__pow__(self, other[, modulo])\n'
+                  'object.__lshift__(self, other)\n'
+                  'object.__rshift__(self, other)\n'
+                  'object.__and__(self, other)\n'
+                  'object.__xor__(self, other)\n'
+                  'object.__or__(self, other)\n'
+                  '\n'
+                  '   These methods are called to implement the binary '
+                  'arithmetic\n'
+                  '   operations ("+", "-", "*", "@", "/", "//", "%", '
+                  '"divmod()",\n'
+                  '   "pow()", "**", "<<", ">>", "&", "^", "|").  For '
+                  'instance, to\n'
+                  '   evaluate the expression "x + y", where *x* is an '
+                  'instance of a\n'
+                  '   class that has an "__add__()" method, "x.__add__(y)" is '
+                  'called.\n'
+                  '   The "__divmod__()" method should be the equivalent to '
+                  'using\n'
+                  '   "__floordiv__()" and "__mod__()"; it should not be '
+                  'related to\n'
+                  '   "__truediv__()".  Note that "__pow__()" should be '
+                  'defined to accept\n'
+                  '   an optional third argument if the ternary version of the '
+                  'built-in\n'
+                  '   "pow()" function is to be supported.\n'
+                  '\n'
+                  '   If one of those methods does not support the operation '
+                  'with the\n'
+                  '   supplied arguments, it should return "NotImplemented".\n'
+                  '\n'
+                  'object.__radd__(self, other)\n'
+                  'object.__rsub__(self, other)\n'
+                  'object.__rmul__(self, other)\n'
+                  'object.__rmatmul__(self, other)\n'
+                  'object.__rtruediv__(self, other)\n'
+                  'object.__rfloordiv__(self, other)\n'
+                  'object.__rmod__(self, other)\n'
+                  'object.__rdivmod__(self, other)\n'
+                  'object.__rpow__(self, other)\n'
+                  'object.__rlshift__(self, other)\n'
+                  'object.__rrshift__(self, other)\n'
+                  'object.__rand__(self, other)\n'
+                  'object.__rxor__(self, other)\n'
+                  'object.__ror__(self, other)\n'
+                  '\n'
+                  '   These methods are called to implement the binary '
+                  'arithmetic\n'
+                  '   operations ("+", "-", "*", "@", "/", "//", "%", '
+                  '"divmod()",\n'
+                  '   "pow()", "**", "<<", ">>", "&", "^", "|") with reflected '
+                  '(swapped)\n'
+                  '   operands.  These functions are only called if the left '
+                  'operand does\n'
+                  '   not support the corresponding operation [3] and the '
+                  'operands are of\n'
+                  '   different types. [4] For instance, to evaluate the '
+                  'expression "x -\n'
+                  '   y", where *y* is an instance of a class that has an '
+                  '"__rsub__()"\n'
+                  '   method, "y.__rsub__(x)" is called if "x.__sub__(y)" '
+                  'returns\n'
+                  '   *NotImplemented*.\n'
+                  '\n'
+                  '   Note that ternary "pow()" will not try calling '
+                  '"__rpow__()" (the\n'
+                  '   coercion rules would become too complicated).\n'
+                  '\n'
+                  '   Note: If the right operand’s type is a subclass of the '
+                  'left\n'
+                  '     operand’s type and that subclass provides the '
+                  'reflected method\n'
+                  '     for the operation, this method will be called before '
+                  'the left\n'
+                  '     operand’s non-reflected method.  This behavior allows '
+                  'subclasses\n'
+                  '     to override their ancestors’ operations.\n'
+                  '\n'
+                  'object.__iadd__(self, other)\n'
+                  'object.__isub__(self, other)\n'
+                  'object.__imul__(self, other)\n'
+                  'object.__imatmul__(self, other)\n'
+                  'object.__itruediv__(self, other)\n'
+                  'object.__ifloordiv__(self, other)\n'
+                  'object.__imod__(self, other)\n'
+                  'object.__ipow__(self, other[, modulo])\n'
+                  'object.__ilshift__(self, other)\n'
+                  'object.__irshift__(self, other)\n'
+                  'object.__iand__(self, other)\n'
+                  'object.__ixor__(self, other)\n'
+                  'object.__ior__(self, other)\n'
+                  '\n'
+                  '   These methods are called to implement the augmented '
+                  'arithmetic\n'
+                  '   assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", '
+                  '"**=",\n'
+                  '   "<<=", ">>=", "&=", "^=", "|=").  These methods should '
+                  'attempt to\n'
+                  '   do the operation in-place (modifying *self*) and return '
+                  'the result\n'
+                  '   (which could be, but does not have to be, *self*).  If a '
+                  'specific\n'
+                  '   method is not defined, the augmented assignment falls '
+                  'back to the\n'
+                  '   normal methods.  For instance, if *x* is an instance of '
+                  'a class\n'
+                  '   with an "__iadd__()" method, "x += y" is equivalent to '
+                  '"x =\n'
+                  '   x.__iadd__(y)" . Otherwise, "x.__add__(y)" and '
+                  '"y.__radd__(x)" are\n'
+                  '   considered, as with the evaluation of "x + y". In '
+                  'certain\n'
+                  '   situations, augmented assignment can result in '
+                  'unexpected errors\n'
+                  '   (see Why does a_tuple[i] += [‘item’] raise an exception '
+                  'when the\n'
+                  '   addition works?), but this behavior is in fact part of '
+                  'the data\n'
+                  '   model.\n'
+                  '\n'
+                  'object.__neg__(self)\n'
+                  'object.__pos__(self)\n'
+                  'object.__abs__(self)\n'
+                  'object.__invert__(self)\n'
+                  '\n'
+                  '   Called to implement the unary arithmetic operations '
+                  '("-", "+",\n'
+                  '   "abs()" and "~").\n'
+                  '\n'
+                  'object.__complex__(self)\n'
+                  'object.__int__(self)\n'
+                  'object.__float__(self)\n'
+                  '\n'
+                  '   Called to implement the built-in functions "complex()", '
+                  '"int()" and\n'
+                  '   "float()".  Should return a value of the appropriate '
+                  'type.\n'
+                  '\n'
+                  'object.__index__(self)\n'
+                  '\n'
+                  '   Called to implement "operator.index()", and whenever '
+                  'Python needs\n'
+                  '   to losslessly convert the numeric object to an integer '
+                  'object (such\n'
+                  '   as in slicing, or in the built-in "bin()", "hex()" and '
+                  '"oct()"\n'
+                  '   functions). Presence of this method indicates that the '
+                  'numeric\n'
+                  '   object is an integer type.  Must return an integer.\n'
+                  '\n'
+                  '   Note: In order to have a coherent integer type class, '
+                  'when\n'
+                  '     "__index__()" is defined "__int__()" should also be '
+                  'defined, and\n'
+                  '     both should return the same value.\n'
+                  '\n'
+                  'object.__round__(self[, ndigits])\n'
+                  'object.__trunc__(self)\n'
+                  'object.__floor__(self)\n'
+                  'object.__ceil__(self)\n'
+                  '\n'
+                  '   Called to implement the built-in function "round()" and '
+                  '"math"\n'
+                  '   functions "trunc()", "floor()" and "ceil()". Unless '
+                  '*ndigits* is\n'
+                  '   passed to "__round__()" all these methods should return '
+                  'the value\n'
+                  '   of the object truncated to an "Integral" (typically an '
+                  '"int").\n'
+                  '\n'
+                  '   If "__int__()" is not defined then the built-in function '
+                  '"int()"\n'
+                  '   falls back to "__trunc__()".\n',
+ 'objects': 'Objects, values and types\n'
+            '*************************\n'
+            '\n'
+            '*Objects* are Python’s abstraction for data.  All data in a '
+            'Python\n'
+            'program is represented by objects or by relations between '
+            'objects. (In\n'
+            'a sense, and in conformance to Von Neumann’s model of a “stored\n'
+            'program computer,” code is also represented by objects.)\n'
+            '\n'
+            'Every object has an identity, a type and a value.  An object’s\n'
+            '*identity* never changes once it has been created; you may think '
+            'of it\n'
+            'as the object’s address in memory.  The ‘"is"’ operator compares '
+            'the\n'
+            'identity of two objects; the "id()" function returns an integer\n'
+            'representing its identity.\n'
+            '\n'
+            '**CPython implementation detail:** For CPython, "id(x)" is the '
+            'memory\n'
+            'address where "x" is stored.\n'
+            '\n'
+            'An object’s type determines the operations that the object '
+            'supports\n'
+            '(e.g., “does it have a length?”) and also defines the possible '
+            'values\n'
+            'for objects of that type.  The "type()" function returns an '
+            'object’s\n'
+            'type (which is an object itself).  Like its identity, an '
+            'object’s\n'
+            '*type* is also unchangeable. [1]\n'
+            '\n'
+            'The *value* of some objects can change.  Objects whose value can\n'
+            'change are said to be *mutable*; objects whose value is '
+            'unchangeable\n'
+            'once they are created are called *immutable*. (The value of an\n'
+            'immutable container object that contains a reference to a '
+            'mutable\n'
+            'object can change when the latter’s value is changed; however '
+            'the\n'
+            'container is still considered immutable, because the collection '
+            'of\n'
+            'objects it contains cannot be changed.  So, immutability is not\n'
+            'strictly the same as having an unchangeable value, it is more '
+            'subtle.)\n'
+            'An object’s mutability is determined by its type; for instance,\n'
+            'numbers, strings and tuples are immutable, while dictionaries '
+            'and\n'
+            'lists are mutable.\n'
+            '\n'
+            'Objects are never explicitly destroyed; however, when they '
+            'become\n'
+            'unreachable they may be garbage-collected.  An implementation is\n'
+            'allowed to postpone garbage collection or omit it altogether — it '
+            'is a\n'
+            'matter of implementation quality how garbage collection is\n'
+            'implemented, as long as no objects are collected that are still\n'
+            'reachable.\n'
+            '\n'
+            '**CPython implementation detail:** CPython currently uses a '
+            'reference-\n'
+            'counting scheme with (optional) delayed detection of cyclically '
+            'linked\n'
+            'garbage, which collects most objects as soon as they become\n'
+            'unreachable, but is not guaranteed to collect garbage containing\n'
+            'circular references.  See the documentation of the "gc" module '
+            'for\n'
+            'information on controlling the collection of cyclic garbage. '
+            'Other\n'
+            'implementations act differently and CPython may change. Do not '
+            'depend\n'
+            'on immediate finalization of objects when they become unreachable '
+            '(so\n'
+            'you should always close files explicitly).\n'
+            '\n'
+            'Note that the use of the implementation’s tracing or debugging\n'
+            'facilities may keep objects alive that would normally be '
+            'collectable.\n'
+            'Also note that catching an exception with a ‘"try"…"except"’ '
+            'statement\n'
+            'may keep objects alive.\n'
+            '\n'
+            'Some objects contain references to “external” resources such as '
+            'open\n'
+            'files or windows.  It is understood that these resources are '
+            'freed\n'
+            'when the object is garbage-collected, but since garbage '
+            'collection is\n'
+            'not guaranteed to happen, such objects also provide an explicit '
+            'way to\n'
+            'release the external resource, usually a "close()" method. '
+            'Programs\n'
+            'are strongly recommended to explicitly close such objects.  The\n'
+            '‘"try"…"finally"’ statement and the ‘"with"’ statement provide\n'
+            'convenient ways to do this.\n'
+            '\n'
+            'Some objects contain references to other objects; these are '
+            'called\n'
+            '*containers*. Examples of containers are tuples, lists and\n'
+            'dictionaries.  The references are part of a container’s value.  '
+            'In\n'
+            'most cases, when we talk about the value of a container, we imply '
+            'the\n'
+            'values, not the identities of the contained objects; however, '
+            'when we\n'
+            'talk about the mutability of a container, only the identities of '
+            'the\n'
+            'immediately contained objects are implied.  So, if an immutable\n'
+            'container (like a tuple) contains a reference to a mutable '
+            'object, its\n'
+            'value changes if that mutable object is changed.\n'
+            '\n'
+            'Types affect almost all aspects of object behavior.  Even the\n'
+            'importance of object identity is affected in some sense: for '
+            'immutable\n'
+            'types, operations that compute new values may actually return a\n'
+            'reference to any existing object with the same type and value, '
+            'while\n'
+            'for mutable objects this is not allowed.  E.g., after "a = 1; b = '
+            '1",\n'
+            '"a" and "b" may or may not refer to the same object with the '
+            'value\n'
+            'one, depending on the implementation, but after "c = []; d = []", '
+            '"c"\n'
+            'and "d" are guaranteed to refer to two different, unique, newly\n'
+            'created empty lists. (Note that "c = d = []" assigns the same '
+            'object\n'
+            'to both "c" and "d".)\n',
+ 'operator-summary': 'Operator precedence\n'
+                     '*******************\n'
+                     '\n'
+                     'The following table summarizes the operator precedence '
+                     'in Python, from\n'
+                     'lowest precedence (least binding) to highest precedence '
+                     '(most\n'
+                     'binding).  Operators in the same box have the same '
+                     'precedence.  Unless\n'
+                     'the syntax is explicitly given, operators are binary.  '
+                     'Operators in\n'
+                     'the same box group left to right (except for '
+                     'exponentiation, which\n'
+                     'groups from right to left).\n'
+                     '\n'
+                     'Note that comparisons, membership tests, and identity '
+                     'tests, all have\n'
+                     'the same precedence and have a left-to-right chaining '
+                     'feature as\n'
+                     'described in the Comparisons section.\n'
+                     '\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| Operator                                        | '
+                     'Description                           |\n'
+                     '+=================================================+=======================================+\n'
+                     '| "lambda"                                        | '
+                     'Lambda expression                     |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "if" – "else"                                   | '
+                     'Conditional expression                |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "or"                                            | '
+                     'Boolean OR                            |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "and"                                           | '
+                     'Boolean AND                           |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "not" "x"                                       | '
+                     'Boolean NOT                           |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "in", "not in", "is", "is not", "<", "<=", ">", | '
+                     'Comparisons, including membership     |\n'
+                     '| ">=", "!=", "=="                                | '
+                     'tests and identity tests              |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "|"                                             | '
+                     'Bitwise OR                            |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "^"                                             | '
+                     'Bitwise XOR                           |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "&"                                             | '
+                     'Bitwise AND                           |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "<<", ">>"                                      | '
+                     'Shifts                                |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "+", "-"                                        | '
+                     'Addition and subtraction              |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "*", "@", "/", "//", "%"                        | '
+                     'Multiplication, matrix                |\n'
+                     '|                                                 | '
+                     'multiplication, division, floor       |\n'
+                     '|                                                 | '
+                     'division, remainder [5]               |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "+x", "-x", "~x"                                | '
+                     'Positive, negative, bitwise NOT       |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "**"                                            | '
+                     'Exponentiation [6]                    |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "await" "x"                                     | '
+                     'Await expression                      |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "x[index]", "x[index:index]",                   | '
+                     'Subscription, slicing, call,          |\n'
+                     '| "x(arguments...)", "x.attribute"                | '
+                     'attribute reference                   |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '| "(expressions...)", "[expressions...]", "{key:  | '
+                     'Binding or tuple display, list        |\n'
+                     '| value...}", "{expressions...}"                  | '
+                     'display, dictionary display, set      |\n'
+                     '|                                                 | '
+                     'display                               |\n'
+                     '+-------------------------------------------------+---------------------------------------+\n'
+                     '\n'
+                     '-[ Footnotes ]-\n'
+                     '\n'
+                     '[1] While "abs(x%y) < abs(y)" is true mathematically, '
+                     'for floats\n'
+                     '    it may not be true numerically due to roundoff.  For '
+                     'example, and\n'
+                     '    assuming a platform on which a Python float is an '
+                     'IEEE 754 double-\n'
+                     '    precision number, in order that "-1e-100 % 1e100" '
+                     'have the same\n'
+                     '    sign as "1e100", the computed result is "-1e-100 + '
+                     '1e100", which\n'
+                     '    is numerically exactly equal to "1e100".  The '
+                     'function\n'
+                     '    "math.fmod()" returns a result whose sign matches '
+                     'the sign of the\n'
+                     '    first argument instead, and so returns "-1e-100" in '
+                     'this case.\n'
+                     '    Which approach is more appropriate depends on the '
+                     'application.\n'
+                     '\n'
+                     '[2] If x is very close to an exact integer multiple of '
+                     'y, it’s\n'
+                     '    possible for "x//y" to be one larger than '
+                     '"(x-x%y)//y" due to\n'
+                     '    rounding.  In such cases, Python returns the latter '
+                     'result, in\n'
+                     '    order to preserve that "divmod(x,y)[0] * y + x % y" '
+                     'be very close\n'
+                     '    to "x".\n'
+                     '\n'
+                     '[3] The Unicode standard distinguishes between *code '
+                     'points* (e.g.\n'
+                     '    U+0041) and *abstract characters* (e.g. “LATIN '
+                     'CAPITAL LETTER A”).\n'
+                     '    While most abstract characters in Unicode are only '
+                     'represented\n'
+                     '    using one code point, there is a number of abstract '
+                     'characters\n'
+                     '    that can in addition be represented using a sequence '
+                     'of more than\n'
+                     '    one code point.  For example, the abstract character '
+                     '“LATIN\n'
+                     '    CAPITAL LETTER C WITH CEDILLA” can be represented as '
+                     'a single\n'
+                     '    *precomposed character* at code position U+00C7, or '
+                     'as a sequence\n'
+                     '    of a *base character* at code position U+0043 (LATIN '
+                     'CAPITAL\n'
+                     '    LETTER C), followed by a *combining character* at '
+                     'code position\n'
+                     '    U+0327 (COMBINING CEDILLA).\n'
+                     '\n'
+                     '    The comparison operators on strings compare at the '
+                     'level of\n'
+                     '    Unicode code points. This may be counter-intuitive '
+                     'to humans.  For\n'
+                     '    example, ""\\u00C7" == "\\u0043\\u0327"" is "False", '
+                     'even though both\n'
+                     '    strings represent the same abstract character “LATIN '
+                     'CAPITAL\n'
+                     '    LETTER C WITH CEDILLA”.\n'
+                     '\n'
+                     '    To compare strings at the level of abstract '
+                     'characters (that is,\n'
+                     '    in a way intuitive to humans), use '
+                     '"unicodedata.normalize()".\n'
+                     '\n'
+                     '[4] Due to automatic garbage-collection, free lists, and '
+                     'the\n'
+                     '    dynamic nature of descriptors, you may notice '
+                     'seemingly unusual\n'
+                     '    behaviour in certain uses of the "is" operator, like '
+                     'those\n'
+                     '    involving comparisons between instance methods, or '
+                     'constants.\n'
+                     '    Check their documentation for more info.\n'
+                     '\n'
+                     '[5] The "%" operator is also used for string formatting; '
+                     'the same\n'
+                     '    precedence applies.\n'
+                     '\n'
+                     '[6] The power operator "**" binds less tightly than an '
+                     'arithmetic\n'
+                     '    or bitwise unary operator on its right, that is, '
+                     '"2**-1" is "0.5".\n',
+ 'pass': 'The "pass" statement\n'
+         '********************\n'
+         '\n'
+         '   pass_stmt ::= "pass"\n'
+         '\n'
+         '"pass" is a null operation — when it is executed, nothing happens. '
+         'It\n'
+         'is useful as a placeholder when a statement is required '
+         'syntactically,\n'
+         'but no code needs to be executed, for example:\n'
+         '\n'
+         '   def f(arg): pass    # a function that does nothing (yet)\n'
+         '\n'
+         '   class C: pass       # a class with no methods (yet)\n',
+ 'power': 'The power operator\n'
+          '******************\n'
+          '\n'
+          'The power operator binds more tightly than unary operators on its\n'
+          'left; it binds less tightly than unary operators on its right.  '
+          'The\n'
+          'syntax is:\n'
+          '\n'
+          '   power ::= (await_expr | primary) ["**" u_expr]\n'
+          '\n'
+          'Thus, in an unparenthesized sequence of power and unary operators, '
+          'the\n'
+          'operators are evaluated from right to left (this does not '
+          'constrain\n'
+          'the evaluation order for the operands): "-1**2" results in "-1".\n'
+          '\n'
+          'The power operator has the same semantics as the built-in "pow()"\n'
+          'function, when called with two arguments: it yields its left '
+          'argument\n'
+          'raised to the power of its right argument.  The numeric arguments '
+          'are\n'
+          'first converted to a common type, and the result is of that type.\n'
+          '\n'
+          'For int operands, the result has the same type as the operands '
+          'unless\n'
+          'the second argument is negative; in that case, all arguments are\n'
+          'converted to float and a float result is delivered. For example,\n'
+          '"10**2" returns "100", but "10**-2" returns "0.01".\n'
+          '\n'
+          'Raising "0.0" to a negative power results in a '
+          '"ZeroDivisionError".\n'
+          'Raising a negative number to a fractional power results in a '
+          '"complex"\n'
+          'number. (In earlier versions it raised a "ValueError".)\n',
+ 'raise': 'The "raise" statement\n'
+          '*********************\n'
+          '\n'
+          '   raise_stmt ::= "raise" [expression ["from" expression]]\n'
+          '\n'
+          'If no expressions are present, "raise" re-raises the last '
+          'exception\n'
+          'that was active in the current scope.  If no exception is active '
+          'in\n'
+          'the current scope, a "RuntimeError" exception is raised indicating\n'
+          'that this is an error.\n'
+          '\n'
+          'Otherwise, "raise" evaluates the first expression as the exception\n'
+          'object.  It must be either a subclass or an instance of\n'
+          '"BaseException". If it is a class, the exception instance will be\n'
+          'obtained when needed by instantiating the class with no arguments.\n'
+          '\n'
+          'The *type* of the exception is the exception instance’s class, the\n'
+          '*value* is the instance itself.\n'
+          '\n'
+          'A traceback object is normally created automatically when an '
+          'exception\n'
+          'is raised and attached to it as the "__traceback__" attribute, '
+          'which\n'
+          'is writable. You can create an exception and set your own traceback '
+          'in\n'
+          'one step using the "with_traceback()" exception method (which '
+          'returns\n'
+          'the same exception instance, with its traceback set to its '
+          'argument),\n'
+          'like so:\n'
+          '\n'
+          '   raise Exception("foo occurred").with_traceback(tracebackobj)\n'
+          '\n'
+          'The "from" clause is used for exception chaining: if given, the '
+          'second\n'
+          '*expression* must be another exception class or instance, which '
+          'will\n'
+          'then be attached to the raised exception as the "__cause__" '
+          'attribute\n'
+          '(which is writable).  If the raised exception is not handled, both\n'
+          'exceptions will be printed:\n'
+          '\n'
+          '   >>> try:\n'
+          '   ...     print(1 / 0)\n'
+          '   ... except Exception as exc:\n'
+          '   ...     raise RuntimeError("Something bad happened") from exc\n'
+          '   ...\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 2, in <module>\n'
+          '   ZeroDivisionError: division by zero\n'
+          '\n'
+          '   The above exception was the direct cause of the following '
+          'exception:\n'
+          '\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 4, in <module>\n'
+          '   RuntimeError: Something bad happened\n'
+          '\n'
+          'A similar mechanism works implicitly if an exception is raised '
+          'inside\n'
+          'an exception handler or a "finally" clause: the previous exception '
+          'is\n'
+          'then attached as the new exception’s "__context__" attribute:\n'
+          '\n'
+          '   >>> try:\n'
+          '   ...     print(1 / 0)\n'
+          '   ... except:\n'
+          '   ...     raise RuntimeError("Something bad happened")\n'
+          '   ...\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 2, in <module>\n'
+          '   ZeroDivisionError: division by zero\n'
+          '\n'
+          '   During handling of the above exception, another exception '
+          'occurred:\n'
+          '\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 4, in <module>\n'
+          '   RuntimeError: Something bad happened\n'
+          '\n'
+          'Exception chaining can be explicitly suppressed by specifying '
+          '"None"\n'
+          'in the "from" clause:\n'
+          '\n'
+          '   >>> try:\n'
+          '   ...     print(1 / 0)\n'
+          '   ... except:\n'
+          '   ...     raise RuntimeError("Something bad happened") from None\n'
+          '   ...\n'
+          '   Traceback (most recent call last):\n'
+          '     File "<stdin>", line 4, in <module>\n'
+          '   RuntimeError: Something bad happened\n'
+          '\n'
+          'Additional information on exceptions can be found in section\n'
+          'Exceptions, and information about handling exceptions is in '
+          'section\n'
+          'The try statement.\n'
+          '\n'
+          'Changed in version 3.3: "None" is now permitted as "Y" in "raise X\n'
+          'from Y".\n'
+          '\n'
+          'New in version 3.3: The "__suppress_context__" attribute to '
+          'suppress\n'
+          'automatic display of the exception context.\n',
+ 'return': 'The "return" statement\n'
+           '**********************\n'
+           '\n'
+           '   return_stmt ::= "return" [expression_list]\n'
+           '\n'
+           '"return" may only occur syntactically nested in a function '
+           'definition,\n'
+           'not within a nested class definition.\n'
+           '\n'
+           'If an expression list is present, it is evaluated, else "None" is\n'
+           'substituted.\n'
+           '\n'
+           '"return" leaves the current function call with the expression list '
+           '(or\n'
+           '"None") as return value.\n'
+           '\n'
+           'When "return" passes control out of a "try" statement with a '
+           '"finally"\n'
+           'clause, that "finally" clause is executed before really leaving '
+           'the\n'
+           'function.\n'
+           '\n'
+           'In a generator function, the "return" statement indicates that '
+           'the\n'
+           'generator is done and will cause "StopIteration" to be raised. '
+           'The\n'
+           'returned value (if any) is used as an argument to construct\n'
+           '"StopIteration" and becomes the "StopIteration.value" attribute.\n'
+           '\n'
+           'In an asynchronous generator function, an empty "return" '
+           'statement\n'
+           'indicates that the asynchronous generator is done and will cause\n'
+           '"StopAsyncIteration" to be raised.  A non-empty "return" statement '
+           'is\n'
+           'a syntax error in an asynchronous generator function.\n',
+ 'sequence-types': 'Emulating container types\n'
+                   '*************************\n'
+                   '\n'
+                   'The following methods can be defined to implement '
+                   'container objects.\n'
+                   'Containers usually are sequences (such as lists or tuples) '
+                   'or mappings\n'
+                   '(like dictionaries), but can represent other containers as '
+                   'well.  The\n'
+                   'first set of methods is used either to emulate a sequence '
+                   'or to\n'
+                   'emulate a mapping; the difference is that for a sequence, '
+                   'the\n'
+                   'allowable keys should be the integers *k* for which "0 <= '
+                   'k < N" where\n'
+                   '*N* is the length of the sequence, or slice objects, which '
+                   'define a\n'
+                   'range of items.  It is also recommended that mappings '
+                   'provide the\n'
+                   'methods "keys()", "values()", "items()", "get()", '
+                   '"clear()",\n'
+                   '"setdefault()", "pop()", "popitem()", "copy()", and '
+                   '"update()"\n'
+                   'behaving similar to those for Python’s standard dictionary '
+                   'objects.\n'
+                   'The "collections" module provides a "MutableMapping" '
+                   'abstract base\n'
+                   'class to help create those methods from a base set of '
+                   '"__getitem__()",\n'
+                   '"__setitem__()", "__delitem__()", and "keys()". Mutable '
+                   'sequences\n'
+                   'should provide methods "append()", "count()", "index()", '
+                   '"extend()",\n'
+                   '"insert()", "pop()", "remove()", "reverse()" and "sort()", '
+                   'like Python\n'
+                   'standard list objects.  Finally, sequence types should '
+                   'implement\n'
+                   'addition (meaning concatenation) and multiplication '
+                   '(meaning\n'
+                   'repetition) by defining the methods "__add__()", '
+                   '"__radd__()",\n'
+                   '"__iadd__()", "__mul__()", "__rmul__()" and "__imul__()" '
+                   'described\n'
+                   'below; they should not define other numerical operators.  '
+                   'It is\n'
+                   'recommended that both mappings and sequences implement '
+                   'the\n'
+                   '"__contains__()" method to allow efficient use of the "in" '
+                   'operator;\n'
+                   'for mappings, "in" should search the mapping’s keys; for '
+                   'sequences, it\n'
+                   'should search through the values.  It is further '
+                   'recommended that both\n'
+                   'mappings and sequences implement the "__iter__()" method '
+                   'to allow\n'
+                   'efficient iteration through the container; for mappings, '
+                   '"__iter__()"\n'
+                   'should be the same as "keys()"; for sequences, it should '
+                   'iterate\n'
+                   'through the values.\n'
+                   '\n'
+                   'object.__len__(self)\n'
+                   '\n'
+                   '   Called to implement the built-in function "len()".  '
+                   'Should return\n'
+                   '   the length of the object, an integer ">=" 0.  Also, an '
+                   'object that\n'
+                   '   doesn’t define a "__bool__()" method and whose '
+                   '"__len__()" method\n'
+                   '   returns zero is considered to be false in a Boolean '
+                   'context.\n'
+                   '\n'
+                   '   **CPython implementation detail:** In CPython, the '
+                   'length is\n'
+                   '   required to be at most "sys.maxsize". If the length is '
+                   'larger than\n'
+                   '   "sys.maxsize" some features (such as "len()") may '
+                   'raise\n'
+                   '   "OverflowError".  To prevent raising "OverflowError" by '
+                   'truth value\n'
+                   '   testing, an object must define a "__bool__()" method.\n'
+                   '\n'
+                   'object.__length_hint__(self)\n'
+                   '\n'
+                   '   Called to implement "operator.length_hint()". Should '
+                   'return an\n'
+                   '   estimated length for the object (which may be greater '
+                   'or less than\n'
+                   '   the actual length). The length must be an integer ">=" '
+                   '0. This\n'
+                   '   method is purely an optimization and is never required '
+                   'for\n'
+                   '   correctness.\n'
+                   '\n'
+                   '   New in version 3.4.\n'
+                   '\n'
+                   'Note: Slicing is done exclusively with the following three '
+                   'methods.\n'
+                   '  A call like\n'
+                   '\n'
+                   '     a[1:2] = b\n'
+                   '\n'
+                   '  is translated to\n'
+                   '\n'
+                   '     a[slice(1, 2, None)] = b\n'
+                   '\n'
+                   '  and so forth.  Missing slice items are always filled in '
+                   'with "None".\n'
+                   '\n'
+                   'object.__getitem__(self, key)\n'
+                   '\n'
+                   '   Called to implement evaluation of "self[key]". For '
+                   'sequence types,\n'
+                   '   the accepted keys should be integers and slice '
+                   'objects.  Note that\n'
+                   '   the special interpretation of negative indexes (if the '
+                   'class wishes\n'
+                   '   to emulate a sequence type) is up to the '
+                   '"__getitem__()" method. If\n'
+                   '   *key* is of an inappropriate type, "TypeError" may be '
+                   'raised; if of\n'
+                   '   a value outside the set of indexes for the sequence '
+                   '(after any\n'
+                   '   special interpretation of negative values), '
+                   '"IndexError" should be\n'
+                   '   raised. For mapping types, if *key* is missing (not in '
+                   'the\n'
+                   '   container), "KeyError" should be raised.\n'
+                   '\n'
+                   '   Note: "for" loops expect that an "IndexError" will be '
+                   'raised for\n'
+                   '     illegal indexes to allow proper detection of the end '
+                   'of the\n'
+                   '     sequence.\n'
+                   '\n'
+                   'object.__setitem__(self, key, value)\n'
+                   '\n'
+                   '   Called to implement assignment to "self[key]".  Same '
+                   'note as for\n'
+                   '   "__getitem__()".  This should only be implemented for '
+                   'mappings if\n'
+                   '   the objects support changes to the values for keys, or '
+                   'if new keys\n'
+                   '   can be added, or for sequences if elements can be '
+                   'replaced.  The\n'
+                   '   same exceptions should be raised for improper *key* '
+                   'values as for\n'
+                   '   the "__getitem__()" method.\n'
+                   '\n'
+                   'object.__delitem__(self, key)\n'
+                   '\n'
+                   '   Called to implement deletion of "self[key]".  Same note '
+                   'as for\n'
+                   '   "__getitem__()".  This should only be implemented for '
+                   'mappings if\n'
+                   '   the objects support removal of keys, or for sequences '
+                   'if elements\n'
+                   '   can be removed from the sequence.  The same exceptions '
+                   'should be\n'
+                   '   raised for improper *key* values as for the '
+                   '"__getitem__()" method.\n'
+                   '\n'
+                   'object.__missing__(self, key)\n'
+                   '\n'
+                   '   Called by "dict"."__getitem__()" to implement '
+                   '"self[key]" for dict\n'
+                   '   subclasses when key is not in the dictionary.\n'
+                   '\n'
+                   'object.__iter__(self)\n'
+                   '\n'
+                   '   This method is called when an iterator is required for '
+                   'a container.\n'
+                   '   This method should return a new iterator object that '
+                   'can iterate\n'
+                   '   over all the objects in the container.  For mappings, '
+                   'it should\n'
+                   '   iterate over the keys of the container.\n'
+                   '\n'
+                   '   Iterator objects also need to implement this method; '
+                   'they are\n'
+                   '   required to return themselves.  For more information on '
+                   'iterator\n'
+                   '   objects, see Iterator Types.\n'
+                   '\n'
+                   'object.__reversed__(self)\n'
+                   '\n'
+                   '   Called (if present) by the "reversed()" built-in to '
+                   'implement\n'
+                   '   reverse iteration.  It should return a new iterator '
+                   'object that\n'
+                   '   iterates over all the objects in the container in '
+                   'reverse order.\n'
+                   '\n'
+                   '   If the "__reversed__()" method is not provided, the '
+                   '"reversed()"\n'
+                   '   built-in will fall back to using the sequence protocol '
+                   '("__len__()"\n'
+                   '   and "__getitem__()").  Objects that support the '
+                   'sequence protocol\n'
+                   '   should only provide "__reversed__()" if they can '
+                   'provide an\n'
+                   '   implementation that is more efficient than the one '
+                   'provided by\n'
+                   '   "reversed()".\n'
+                   '\n'
+                   'The membership test operators ("in" and "not in") are '
+                   'normally\n'
+                   'implemented as an iteration through a sequence.  However, '
+                   'container\n'
+                   'objects can supply the following special method with a '
+                   'more efficient\n'
+                   'implementation, which also does not require the object be '
+                   'a sequence.\n'
+                   '\n'
+                   'object.__contains__(self, item)\n'
+                   '\n'
+                   '   Called to implement membership test operators.  Should '
+                   'return true\n'
+                   '   if *item* is in *self*, false otherwise.  For mapping '
+                   'objects, this\n'
+                   '   should consider the keys of the mapping rather than the '
+                   'values or\n'
+                   '   the key-item pairs.\n'
+                   '\n'
+                   '   For objects that don’t define "__contains__()", the '
+                   'membership test\n'
+                   '   first tries iteration via "__iter__()", then the old '
+                   'sequence\n'
+                   '   iteration protocol via "__getitem__()", see this '
+                   'section in the\n'
+                   '   language reference.\n',
+ 'shifting': 'Shifting operations\n'
+             '*******************\n'
+             '\n'
+             'The shifting operations have lower priority than the arithmetic\n'
+             'operations:\n'
+             '\n'
+             '   shift_expr ::= a_expr | shift_expr ("<<" | ">>") a_expr\n'
+             '\n'
+             'These operators accept integers as arguments.  They shift the '
+             'first\n'
+             'argument to the left or right by the number of bits given by '
+             'the\n'
+             'second argument.\n'
+             '\n'
+             'A right shift by *n* bits is defined as floor division by '
+             '"pow(2,n)".\n'
+             'A left shift by *n* bits is defined as multiplication with '
+             '"pow(2,n)".\n'
+             '\n'
+             'Note: In the current implementation, the right-hand operand is\n'
+             '  required to be at most "sys.maxsize".  If the right-hand '
+             'operand is\n'
+             '  larger than "sys.maxsize" an "OverflowError" exception is '
+             'raised.\n',
+ 'slicings': 'Slicings\n'
+             '********\n'
+             '\n'
+             'A slicing selects a range of items in a sequence object (e.g., '
+             'a\n'
+             'string, tuple or list).  Slicings may be used as expressions or '
+             'as\n'
+             'targets in assignment or "del" statements.  The syntax for a '
+             'slicing:\n'
+             '\n'
+             '   slicing      ::= primary "[" slice_list "]"\n'
+             '   slice_list   ::= slice_item ("," slice_item)* [","]\n'
+             '   slice_item   ::= expression | proper_slice\n'
+             '   proper_slice ::= [lower_bound] ":" [upper_bound] [ ":" '
+             '[stride] ]\n'
+             '   lower_bound  ::= expression\n'
+             '   upper_bound  ::= expression\n'
+             '   stride       ::= expression\n'
+             '\n'
+             'There is ambiguity in the formal syntax here: anything that '
+             'looks like\n'
+             'an expression list also looks like a slice list, so any '
+             'subscription\n'
+             'can be interpreted as a slicing.  Rather than further '
+             'complicating the\n'
+             'syntax, this is disambiguated by defining that in this case the\n'
+             'interpretation as a subscription takes priority over the\n'
+             'interpretation as a slicing (this is the case if the slice list\n'
+             'contains no proper slice).\n'
+             '\n'
+             'The semantics for a slicing are as follows.  The primary is '
+             'indexed\n'
+             '(using the same "__getitem__()" method as normal subscription) '
+             'with a\n'
+             'key that is constructed from the slice list, as follows.  If the '
+             'slice\n'
+             'list contains at least one comma, the key is a tuple containing '
+             'the\n'
+             'conversion of the slice items; otherwise, the conversion of the '
+             'lone\n'
+             'slice item is the key.  The conversion of a slice item that is '
+             'an\n'
+             'expression is that expression.  The conversion of a proper slice '
+             'is a\n'
+             'slice object (see section The standard type hierarchy) whose '
+             '"start",\n'
+             '"stop" and "step" attributes are the values of the expressions '
+             'given\n'
+             'as lower bound, upper bound and stride, respectively, '
+             'substituting\n'
+             '"None" for missing expressions.\n',
+ 'specialattrs': 'Special Attributes\n'
+                 '******************\n'
+                 '\n'
+                 'The implementation adds a few special read-only attributes '
+                 'to several\n'
+                 'object types, where they are relevant.  Some of these are '
+                 'not reported\n'
+                 'by the "dir()" built-in function.\n'
+                 '\n'
+                 'object.__dict__\n'
+                 '\n'
+                 '   A dictionary or other mapping object used to store an '
+                 'object’s\n'
+                 '   (writable) attributes.\n'
+                 '\n'
+                 'instance.__class__\n'
+                 '\n'
+                 '   The class to which a class instance belongs.\n'
+                 '\n'
+                 'class.__bases__\n'
+                 '\n'
+                 '   The tuple of base classes of a class object.\n'
+                 '\n'
+                 'definition.__name__\n'
+                 '\n'
+                 '   The name of the class, function, method, descriptor, or '
+                 'generator\n'
+                 '   instance.\n'
+                 '\n'
+                 'definition.__qualname__\n'
+                 '\n'
+                 '   The *qualified name* of the class, function, method, '
+                 'descriptor, or\n'
+                 '   generator instance.\n'
+                 '\n'
+                 '   New in version 3.3.\n'
+                 '\n'
+                 'class.__mro__\n'
+                 '\n'
+                 '   This attribute is a tuple of classes that are considered '
+                 'when\n'
+                 '   looking for base classes during method resolution.\n'
+                 '\n'
+                 'class.mro()\n'
+                 '\n'
+                 '   This method can be overridden by a metaclass to customize '
+                 'the\n'
+                 '   method resolution order for its instances.  It is called '
+                 'at class\n'
+                 '   instantiation, and its result is stored in "__mro__".\n'
+                 '\n'
+                 'class.__subclasses__()\n'
+                 '\n'
+                 '   Each class keeps a list of weak references to its '
+                 'immediate\n'
+                 '   subclasses.  This method returns a list of all those '
+                 'references\n'
+                 '   still alive. Example:\n'
+                 '\n'
+                 '      >>> int.__subclasses__()\n'
+                 "      [<class 'bool'>]\n"
+                 '\n'
+                 '-[ Footnotes ]-\n'
+                 '\n'
+                 '[1] Additional information on these special methods may be '
+                 'found\n'
+                 '    in the Python Reference Manual (Basic customization).\n'
+                 '\n'
+                 '[2] As a consequence, the list "[1, 2]" is considered equal '
+                 'to\n'
+                 '    "[1.0, 2.0]", and similarly for tuples.\n'
+                 '\n'
+                 '[3] They must have since the parser can’t tell the type of '
+                 'the\n'
+                 '    operands.\n'
+                 '\n'
+                 '[4] Cased characters are those with general category '
+                 'property\n'
+                 '    being one of “Lu” (Letter, uppercase), “Ll” (Letter, '
+                 'lowercase),\n'
+                 '    or “Lt” (Letter, titlecase).\n'
+                 '\n'
+                 '[5] To format only a tuple you should therefore provide a\n'
+                 '    singleton tuple whose only element is the tuple to be '
+                 'formatted.\n',
+ 'specialnames': 'Special method names\n'
+                 '********************\n'
+                 '\n'
+                 'A class can implement certain operations that are invoked by '
+                 'special\n'
+                 'syntax (such as arithmetic operations or subscripting and '
+                 'slicing) by\n'
+                 'defining methods with special names. This is Python’s '
+                 'approach to\n'
+                 '*operator overloading*, allowing classes to define their own '
+                 'behavior\n'
+                 'with respect to language operators.  For instance, if a '
+                 'class defines\n'
+                 'a method named "__getitem__()", and "x" is an instance of '
+                 'this class,\n'
+                 'then "x[i]" is roughly equivalent to "type(x).__getitem__(x, '
+                 'i)".\n'
+                 'Except where mentioned, attempts to execute an operation '
+                 'raise an\n'
+                 'exception when no appropriate method is defined (typically\n'
+                 '"AttributeError" or "TypeError").\n'
+                 '\n'
+                 'Setting a special method to "None" indicates that the '
+                 'corresponding\n'
+                 'operation is not available.  For example, if a class sets '
+                 '"__iter__()"\n'
+                 'to "None", the class is not iterable, so calling "iter()" on '
+                 'its\n'
+                 'instances will raise a "TypeError" (without falling back to\n'
+                 '"__getitem__()"). [2]\n'
+                 '\n'
+                 'When implementing a class that emulates any built-in type, '
+                 'it is\n'
+                 'important that the emulation only be implemented to the '
+                 'degree that it\n'
+                 'makes sense for the object being modelled.  For example, '
+                 'some\n'
+                 'sequences may work well with retrieval of individual '
+                 'elements, but\n'
+                 'extracting a slice may not make sense.  (One example of this '
+                 'is the\n'
+                 '"NodeList" interface in the W3C’s Document Object Model.)\n'
+                 '\n'
+                 '\n'
+                 'Basic customization\n'
+                 '===================\n'
+                 '\n'
+                 'object.__new__(cls[, ...])\n'
+                 '\n'
+                 '   Called to create a new instance of class *cls*.  '
+                 '"__new__()" is a\n'
+                 '   static method (special-cased so you need not declare it '
+                 'as such)\n'
+                 '   that takes the class of which an instance was requested '
+                 'as its\n'
+                 '   first argument.  The remaining arguments are those passed '
+                 'to the\n'
+                 '   object constructor expression (the call to the class).  '
+                 'The return\n'
+                 '   value of "__new__()" should be the new object instance '
+                 '(usually an\n'
+                 '   instance of *cls*).\n'
+                 '\n'
+                 '   Typical implementations create a new instance of the '
+                 'class by\n'
+                 '   invoking the superclass’s "__new__()" method using\n'
+                 '   "super().__new__(cls[, ...])" with appropriate arguments '
+                 'and then\n'
+                 '   modifying the newly-created instance as necessary before '
+                 'returning\n'
+                 '   it.\n'
+                 '\n'
+                 '   If "__new__()" returns an instance of *cls*, then the '
+                 'new\n'
+                 '   instance’s "__init__()" method will be invoked like\n'
+                 '   "__init__(self[, ...])", where *self* is the new instance '
+                 'and the\n'
+                 '   remaining arguments are the same as were passed to '
+                 '"__new__()".\n'
+                 '\n'
+                 '   If "__new__()" does not return an instance of *cls*, then '
+                 'the new\n'
+                 '   instance’s "__init__()" method will not be invoked.\n'
+                 '\n'
+                 '   "__new__()" is intended mainly to allow subclasses of '
+                 'immutable\n'
+                 '   types (like int, str, or tuple) to customize instance '
+                 'creation.  It\n'
+                 '   is also commonly overridden in custom metaclasses in '
+                 'order to\n'
+                 '   customize class creation.\n'
+                 '\n'
+                 'object.__init__(self[, ...])\n'
+                 '\n'
+                 '   Called after the instance has been created (by '
+                 '"__new__()"), but\n'
+                 '   before it is returned to the caller.  The arguments are '
+                 'those\n'
+                 '   passed to the class constructor expression.  If a base '
+                 'class has an\n'
+                 '   "__init__()" method, the derived class’s "__init__()" '
+                 'method, if\n'
+                 '   any, must explicitly call it to ensure proper '
+                 'initialization of the\n'
+                 '   base class part of the instance; for example:\n'
+                 '   "super().__init__([args...])".\n'
+                 '\n'
+                 '   Because "__new__()" and "__init__()" work together in '
+                 'constructing\n'
+                 '   objects ("__new__()" to create it, and "__init__()" to '
+                 'customize\n'
+                 '   it), no non-"None" value may be returned by "__init__()"; '
+                 'doing so\n'
+                 '   will cause a "TypeError" to be raised at runtime.\n'
+                 '\n'
+                 'object.__del__(self)\n'
+                 '\n'
+                 '   Called when the instance is about to be destroyed.  This '
+                 'is also\n'
+                 '   called a finalizer or (improperly) a destructor.  If a '
+                 'base class\n'
+                 '   has a "__del__()" method, the derived class’s "__del__()" '
+                 'method,\n'
+                 '   if any, must explicitly call it to ensure proper deletion '
+                 'of the\n'
+                 '   base class part of the instance.\n'
+                 '\n'
+                 '   It is possible (though not recommended!) for the '
+                 '"__del__()" method\n'
+                 '   to postpone destruction of the instance by creating a new '
+                 'reference\n'
+                 '   to it.  This is called object *resurrection*.  It is\n'
+                 '   implementation-dependent whether "__del__()" is called a '
+                 'second\n'
+                 '   time when a resurrected object is about to be destroyed; '
+                 'the\n'
+                 '   current *CPython* implementation only calls it once.\n'
+                 '\n'
+                 '   It is not guaranteed that "__del__()" methods are called '
+                 'for\n'
+                 '   objects that still exist when the interpreter exits.\n'
+                 '\n'
+                 '   Note: "del x" doesn’t directly call "x.__del__()" — the '
+                 'former\n'
+                 '     decrements the reference count for "x" by one, and the '
+                 'latter is\n'
+                 '     only called when "x"’s reference count reaches zero.\n'
+                 '\n'
+                 '   **CPython implementation detail:** It is possible for a '
+                 'reference\n'
+                 '   cycle to prevent the reference count of an object from '
+                 'going to\n'
+                 '   zero.  In this case, the cycle will be later detected and '
+                 'deleted\n'
+                 '   by the *cyclic garbage collector*.  A common cause of '
+                 'reference\n'
+                 '   cycles is when an exception has been caught in a local '
+                 'variable.\n'
+                 '   The frame’s locals then reference the exception, which '
+                 'references\n'
+                 '   its own traceback, which references the locals of all '
+                 'frames caught\n'
+                 '   in the traceback.\n'
+                 '\n'
+                 '   See also: Documentation for the "gc" module.\n'
+                 '\n'
+                 '   Warning: Due to the precarious circumstances under which\n'
+                 '     "__del__()" methods are invoked, exceptions that occur '
+                 'during\n'
+                 '     their execution are ignored, and a warning is printed '
+                 'to\n'
+                 '     "sys.stderr" instead. In particular:\n'
+                 '\n'
+                 '     * "__del__()" can be invoked when arbitrary code is '
+                 'being\n'
+                 '       executed, including from any arbitrary thread.  If '
+                 '"__del__()"\n'
+                 '       needs to take a lock or invoke any other blocking '
+                 'resource, it\n'
+                 '       may deadlock as the resource may already be taken by '
+                 'the code\n'
+                 '       that gets interrupted to execute "__del__()".\n'
+                 '\n'
+                 '     * "__del__()" can be executed during interpreter '
+                 'shutdown.  As\n'
+                 '       a consequence, the global variables it needs to '
+                 'access\n'
+                 '       (including other modules) may already have been '
+                 'deleted or set\n'
+                 '       to "None". Python guarantees that globals whose name '
+                 'begins\n'
+                 '       with a single underscore are deleted from their '
+                 'module before\n'
+                 '       other globals are deleted; if no other references to '
+                 'such\n'
+                 '       globals exist, this may help in assuring that '
+                 'imported modules\n'
+                 '       are still available at the time when the "__del__()" '
+                 'method is\n'
+                 '       called.\n'
+                 '\n'
+                 'object.__repr__(self)\n'
+                 '\n'
+                 '   Called by the "repr()" built-in function to compute the '
+                 '“official”\n'
+                 '   string representation of an object.  If at all possible, '
+                 'this\n'
+                 '   should look like a valid Python expression that could be '
+                 'used to\n'
+                 '   recreate an object with the same value (given an '
+                 'appropriate\n'
+                 '   environment).  If this is not possible, a string of the '
+                 'form\n'
+                 '   "<...some useful description...>" should be returned. The '
+                 'return\n'
+                 '   value must be a string object. If a class defines '
+                 '"__repr__()" but\n'
+                 '   not "__str__()", then "__repr__()" is also used when an '
+                 '“informal”\n'
+                 '   string representation of instances of that class is '
+                 'required.\n'
+                 '\n'
+                 '   This is typically used for debugging, so it is important '
+                 'that the\n'
+                 '   representation is information-rich and unambiguous.\n'
+                 '\n'
+                 'object.__str__(self)\n'
+                 '\n'
+                 '   Called by "str(object)" and the built-in functions '
+                 '"format()" and\n'
+                 '   "print()" to compute the “informal” or nicely printable '
+                 'string\n'
+                 '   representation of an object.  The return value must be a '
+                 'string\n'
+                 '   object.\n'
+                 '\n'
+                 '   This method differs from "object.__repr__()" in that '
+                 'there is no\n'
+                 '   expectation that "__str__()" return a valid Python '
+                 'expression: a\n'
+                 '   more convenient or concise representation can be used.\n'
+                 '\n'
+                 '   The default implementation defined by the built-in type '
+                 '"object"\n'
+                 '   calls "object.__repr__()".\n'
+                 '\n'
+                 'object.__bytes__(self)\n'
+                 '\n'
+                 '   Called by bytes to compute a byte-string representation '
+                 'of an\n'
+                 '   object. This should return a "bytes" object.\n'
+                 '\n'
+                 'object.__format__(self, format_spec)\n'
+                 '\n'
+                 '   Called by the "format()" built-in function, and by '
+                 'extension,\n'
+                 '   evaluation of formatted string literals and the '
+                 '"str.format()"\n'
+                 '   method, to produce a “formatted” string representation of '
+                 'an\n'
+                 '   object. The "format_spec" argument is a string that '
+                 'contains a\n'
+                 '   description of the formatting options desired. The '
+                 'interpretation\n'
+                 '   of the "format_spec" argument is up to the type '
+                 'implementing\n'
+                 '   "__format__()", however most classes will either '
+                 'delegate\n'
+                 '   formatting to one of the built-in types, or use a '
+                 'similar\n'
+                 '   formatting option syntax.\n'
+                 '\n'
+                 '   See Format Specification Mini-Language for a description '
+                 'of the\n'
+                 '   standard formatting syntax.\n'
+                 '\n'
+                 '   The return value must be a string object.\n'
+                 '\n'
+                 '   Changed in version 3.4: The __format__ method of "object" '
+                 'itself\n'
+                 '   raises a "TypeError" if passed any non-empty string.\n'
+                 '\n'
+                 'object.__lt__(self, other)\n'
+                 'object.__le__(self, other)\n'
+                 'object.__eq__(self, other)\n'
+                 'object.__ne__(self, other)\n'
+                 'object.__gt__(self, other)\n'
+                 'object.__ge__(self, other)\n'
+                 '\n'
+                 '   These are the so-called “rich comparison” methods. The\n'
+                 '   correspondence between operator symbols and method names '
+                 'is as\n'
+                 '   follows: "x<y" calls "x.__lt__(y)", "x<=y" calls '
+                 '"x.__le__(y)",\n'
+                 '   "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", '
+                 '"x>y" calls\n'
+                 '   "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n'
+                 '\n'
+                 '   A rich comparison method may return the singleton '
+                 '"NotImplemented"\n'
+                 '   if it does not implement the operation for a given pair '
+                 'of\n'
+                 '   arguments. By convention, "False" and "True" are returned '
+                 'for a\n'
+                 '   successful comparison. However, these methods can return '
+                 'any value,\n'
+                 '   so if the comparison operator is used in a Boolean '
+                 'context (e.g.,\n'
+                 '   in the condition of an "if" statement), Python will call '
+                 '"bool()"\n'
+                 '   on the value to determine if the result is true or '
+                 'false.\n'
+                 '\n'
+                 '   By default, "__ne__()" delegates to "__eq__()" and '
+                 'inverts the\n'
+                 '   result unless it is "NotImplemented".  There are no other '
+                 'implied\n'
+                 '   relationships among the comparison operators, for '
+                 'example, the\n'
+                 '   truth of "(x<y or x==y)" does not imply "x<=y". To '
+                 'automatically\n'
+                 '   generate ordering operations from a single root '
+                 'operation, see\n'
+                 '   "functools.total_ordering()".\n'
+                 '\n'
+                 '   See the paragraph on "__hash__()" for some important '
+                 'notes on\n'
+                 '   creating *hashable* objects which support custom '
+                 'comparison\n'
+                 '   operations and are usable as dictionary keys.\n'
+                 '\n'
+                 '   There are no swapped-argument versions of these methods '
+                 '(to be used\n'
+                 '   when the left argument does not support the operation but '
+                 'the right\n'
+                 '   argument does); rather, "__lt__()" and "__gt__()" are '
+                 'each other’s\n'
+                 '   reflection, "__le__()" and "__ge__()" are each other’s '
+                 'reflection,\n'
+                 '   and "__eq__()" and "__ne__()" are their own reflection. '
+                 'If the\n'
+                 '   operands are of different types, and right operand’s type '
+                 'is a\n'
+                 '   direct or indirect subclass of the left operand’s type, '
+                 'the\n'
+                 '   reflected method of the right operand has priority, '
+                 'otherwise the\n'
+                 '   left operand’s method has priority.  Virtual subclassing '
+                 'is not\n'
+                 '   considered.\n'
+                 '\n'
+                 'object.__hash__(self)\n'
+                 '\n'
+                 '   Called by built-in function "hash()" and for operations '
+                 'on members\n'
+                 '   of hashed collections including "set", "frozenset", and '
+                 '"dict".\n'
+                 '   "__hash__()" should return an integer. The only required '
+                 'property\n'
+                 '   is that objects which compare equal have the same hash '
+                 'value; it is\n'
+                 '   advised to mix together the hash values of the components '
+                 'of the\n'
+                 '   object that also play a part in comparison of objects by '
+                 'packing\n'
+                 '   them into a tuple and hashing the tuple. Example:\n'
+                 '\n'
+                 '      def __hash__(self):\n'
+                 '          return hash((self.name, self.nick, self.color))\n'
+                 '\n'
+                 '   Note: "hash()" truncates the value returned from an '
+                 'object’s\n'
+                 '     custom "__hash__()" method to the size of a '
+                 '"Py_ssize_t".  This\n'
+                 '     is typically 8 bytes on 64-bit builds and 4 bytes on '
+                 '32-bit\n'
+                 '     builds. If an object’s   "__hash__()" must interoperate '
+                 'on builds\n'
+                 '     of different bit sizes, be sure to check the width on '
+                 'all\n'
+                 '     supported builds.  An easy way to do this is with '
+                 '"python -c\n'
+                 '     "import sys; print(sys.hash_info.width)"".\n'
+                 '\n'
+                 '   If a class does not define an "__eq__()" method it should '
+                 'not\n'
+                 '   define a "__hash__()" operation either; if it defines '
+                 '"__eq__()"\n'
+                 '   but not "__hash__()", its instances will not be usable as '
+                 'items in\n'
+                 '   hashable collections.  If a class defines mutable objects '
+                 'and\n'
+                 '   implements an "__eq__()" method, it should not implement\n'
+                 '   "__hash__()", since the implementation of hashable '
+                 'collections\n'
+                 '   requires that a key’s hash value is immutable (if the '
+                 'object’s hash\n'
+                 '   value changes, it will be in the wrong hash bucket).\n'
+                 '\n'
+                 '   User-defined classes have "__eq__()" and "__hash__()" '
+                 'methods by\n'
+                 '   default; with them, all objects compare unequal (except '
+                 'with\n'
+                 '   themselves) and "x.__hash__()" returns an appropriate '
+                 'value such\n'
+                 '   that "x == y" implies both that "x is y" and "hash(x) == '
+                 'hash(y)".\n'
+                 '\n'
+                 '   A class that overrides "__eq__()" and does not define '
+                 '"__hash__()"\n'
+                 '   will have its "__hash__()" implicitly set to "None".  '
+                 'When the\n'
+                 '   "__hash__()" method of a class is "None", instances of '
+                 'the class\n'
+                 '   will raise an appropriate "TypeError" when a program '
+                 'attempts to\n'
+                 '   retrieve their hash value, and will also be correctly '
+                 'identified as\n'
+                 '   unhashable when checking "isinstance(obj, '
+                 'collections.Hashable)".\n'
+                 '\n'
+                 '   If a class that overrides "__eq__()" needs to retain the\n'
+                 '   implementation of "__hash__()" from a parent class, the '
+                 'interpreter\n'
+                 '   must be told this explicitly by setting "__hash__ =\n'
+                 '   <ParentClass>.__hash__".\n'
+                 '\n'
+                 '   If a class that does not override "__eq__()" wishes to '
+                 'suppress\n'
+                 '   hash support, it should include "__hash__ = None" in the '
+                 'class\n'
+                 '   definition. A class which defines its own "__hash__()" '
+                 'that\n'
+                 '   explicitly raises a "TypeError" would be incorrectly '
+                 'identified as\n'
+                 '   hashable by an "isinstance(obj, collections.Hashable)" '
+                 'call.\n'
+                 '\n'
+                 '   Note: By default, the "__hash__()" values of str, bytes '
+                 'and\n'
+                 '     datetime objects are “salted” with an unpredictable '
+                 'random value.\n'
+                 '     Although they remain constant within an individual '
+                 'Python\n'
+                 '     process, they are not predictable between repeated '
+                 'invocations of\n'
+                 '     Python.This is intended to provide protection against a '
+                 'denial-\n'
+                 '     of-service caused by carefully-chosen inputs that '
+                 'exploit the\n'
+                 '     worst case performance of a dict insertion, O(n^2) '
+                 'complexity.\n'
+                 '     See http://www.ocert.org/advisories/ocert-2011-003.html '
+                 'for\n'
+                 '     details.Changing hash values affects the iteration '
+                 'order of\n'
+                 '     dicts, sets and other mappings.  Python has never made '
+                 'guarantees\n'
+                 '     about this ordering (and it typically varies between '
+                 '32-bit and\n'
+                 '     64-bit builds).See also "PYTHONHASHSEED".\n'
+                 '\n'
+                 '   Changed in version 3.3: Hash randomization is enabled by '
+                 'default.\n'
+                 '\n'
+                 'object.__bool__(self)\n'
+                 '\n'
+                 '   Called to implement truth value testing and the built-in '
+                 'operation\n'
+                 '   "bool()"; should return "False" or "True".  When this '
+                 'method is not\n'
+                 '   defined, "__len__()" is called, if it is defined, and the '
+                 'object is\n'
+                 '   considered true if its result is nonzero.  If a class '
+                 'defines\n'
+                 '   neither "__len__()" nor "__bool__()", all its instances '
+                 'are\n'
+                 '   considered true.\n'
+                 '\n'
+                 '\n'
+                 'Customizing attribute access\n'
+                 '============================\n'
+                 '\n'
+                 'The following methods can be defined to customize the '
+                 'meaning of\n'
+                 'attribute access (use of, assignment to, or deletion of '
+                 '"x.name") for\n'
+                 'class instances.\n'
+                 '\n'
+                 'object.__getattr__(self, name)\n'
+                 '\n'
+                 '   Called when the default attribute access fails with an\n'
+                 '   "AttributeError" (either "__getattribute__()" raises an\n'
+                 '   "AttributeError" because *name* is not an instance '
+                 'attribute or an\n'
+                 '   attribute in the class tree for "self"; or "__get__()" of '
+                 'a *name*\n'
+                 '   property raises "AttributeError").  This method should '
+                 'either\n'
+                 '   return the (computed) attribute value or raise an '
+                 '"AttributeError"\n'
+                 '   exception.\n'
+                 '\n'
+                 '   Note that if the attribute is found through the normal '
+                 'mechanism,\n'
+                 '   "__getattr__()" is not called.  (This is an intentional '
+                 'asymmetry\n'
+                 '   between "__getattr__()" and "__setattr__()".) This is '
+                 'done both for\n'
+                 '   efficiency reasons and because otherwise "__getattr__()" '
+                 'would have\n'
+                 '   no way to access other attributes of the instance.  Note '
+                 'that at\n'
+                 '   least for instance variables, you can fake total control '
+                 'by not\n'
+                 '   inserting any values in the instance attribute dictionary '
+                 '(but\n'
+                 '   instead inserting them in another object).  See the\n'
+                 '   "__getattribute__()" method below for a way to actually '
+                 'get total\n'
+                 '   control over attribute access.\n'
+                 '\n'
+                 'object.__getattribute__(self, name)\n'
+                 '\n'
+                 '   Called unconditionally to implement attribute accesses '
+                 'for\n'
+                 '   instances of the class. If the class also defines '
+                 '"__getattr__()",\n'
+                 '   the latter will not be called unless "__getattribute__()" '
+                 'either\n'
+                 '   calls it explicitly or raises an "AttributeError". This '
+                 'method\n'
+                 '   should return the (computed) attribute value or raise an\n'
+                 '   "AttributeError" exception. In order to avoid infinite '
+                 'recursion in\n'
+                 '   this method, its implementation should always call the '
+                 'base class\n'
+                 '   method with the same name to access any attributes it '
+                 'needs, for\n'
+                 '   example, "object.__getattribute__(self, name)".\n'
+                 '\n'
+                 '   Note: This method may still be bypassed when looking up '
+                 'special\n'
+                 '     methods as the result of implicit invocation via '
+                 'language syntax\n'
+                 '     or built-in functions. See Special method lookup.\n'
+                 '\n'
+                 'object.__setattr__(self, name, value)\n'
+                 '\n'
+                 '   Called when an attribute assignment is attempted.  This '
+                 'is called\n'
+                 '   instead of the normal mechanism (i.e. store the value in '
+                 'the\n'
+                 '   instance dictionary). *name* is the attribute name, '
+                 '*value* is the\n'
+                 '   value to be assigned to it.\n'
+                 '\n'
+                 '   If "__setattr__()" wants to assign to an instance '
+                 'attribute, it\n'
+                 '   should call the base class method with the same name, for '
+                 'example,\n'
+                 '   "object.__setattr__(self, name, value)".\n'
+                 '\n'
+                 'object.__delattr__(self, name)\n'
+                 '\n'
+                 '   Like "__setattr__()" but for attribute deletion instead '
+                 'of\n'
+                 '   assignment.  This should only be implemented if "del '
+                 'obj.name" is\n'
+                 '   meaningful for the object.\n'
+                 '\n'
+                 'object.__dir__(self)\n'
+                 '\n'
+                 '   Called when "dir()" is called on the object. A sequence '
+                 'must be\n'
+                 '   returned. "dir()" converts the returned sequence to a '
+                 'list and\n'
+                 '   sorts it.\n'
+                 '\n'
+                 '\n'
+                 'Customizing module attribute access\n'
+                 '-----------------------------------\n'
+                 '\n'
+                 'For a more fine grained customization of the module behavior '
+                 '(setting\n'
+                 'attributes, properties, etc.), one can set the "__class__" '
+                 'attribute\n'
+                 'of a module object to a subclass of "types.ModuleType". For '
+                 'example:\n'
+                 '\n'
+                 '   import sys\n'
+                 '   from types import ModuleType\n'
+                 '\n'
+                 '   class VerboseModule(ModuleType):\n'
+                 '       def __repr__(self):\n'
+                 "           return f'Verbose {self.__name__}'\n"
+                 '\n'
+                 '       def __setattr__(self, attr, value):\n'
+                 "           print(f'Setting {attr}...')\n"
+                 '           setattr(self, attr, value)\n'
+                 '\n'
+                 '   sys.modules[__name__].__class__ = VerboseModule\n'
+                 '\n'
+                 'Note: Setting module "__class__" only affects lookups made '
+                 'using the\n'
+                 '  attribute access syntax – directly accessing the module '
+                 'globals\n'
+                 '  (whether by code within the module, or via a reference to '
+                 'the\n'
+                 '  module’s globals dictionary) is unaffected.\n'
+                 '\n'
+                 'Changed in version 3.5: "__class__" module attribute is now '
+                 'writable.\n'
+                 '\n'
+                 '\n'
+                 'Implementing Descriptors\n'
+                 '------------------------\n'
+                 '\n'
+                 'The following methods only apply when an instance of the '
+                 'class\n'
+                 'containing the method (a so-called *descriptor* class) '
+                 'appears in an\n'
+                 '*owner* class (the descriptor must be in either the owner’s '
+                 'class\n'
+                 'dictionary or in the class dictionary for one of its '
+                 'parents).  In the\n'
+                 'examples below, “the attribute” refers to the attribute '
+                 'whose name is\n'
+                 'the key of the property in the owner class’ "__dict__".\n'
+                 '\n'
+                 'object.__get__(self, instance, owner)\n'
+                 '\n'
+                 '   Called to get the attribute of the owner class (class '
+                 'attribute\n'
+                 '   access) or of an instance of that class (instance '
+                 'attribute\n'
+                 '   access). *owner* is always the owner class, while '
+                 '*instance* is the\n'
+                 '   instance that the attribute was accessed through, or '
+                 '"None" when\n'
+                 '   the attribute is accessed through the *owner*.  This '
+                 'method should\n'
+                 '   return the (computed) attribute value or raise an '
+                 '"AttributeError"\n'
+                 '   exception.\n'
+                 '\n'
+                 'object.__set__(self, instance, value)\n'
+                 '\n'
+                 '   Called to set the attribute on an instance *instance* of '
+                 'the owner\n'
+                 '   class to a new value, *value*.\n'
+                 '\n'
+                 'object.__delete__(self, instance)\n'
+                 '\n'
+                 '   Called to delete the attribute on an instance *instance* '
+                 'of the\n'
+                 '   owner class.\n'
+                 '\n'
+                 'object.__set_name__(self, owner, name)\n'
+                 '\n'
+                 '   Called at the time the owning class *owner* is created. '
+                 'The\n'
+                 '   descriptor has been assigned to *name*.\n'
+                 '\n'
+                 '   New in version 3.6.\n'
+                 '\n'
+                 'The attribute "__objclass__" is interpreted by the "inspect" '
+                 'module as\n'
+                 'specifying the class where this object was defined (setting '
+                 'this\n'
+                 'appropriately can assist in runtime introspection of dynamic '
+                 'class\n'
+                 'attributes). For callables, it may indicate that an instance '
+                 'of the\n'
+                 'given type (or a subclass) is expected or required as the '
+                 'first\n'
+                 'positional argument (for example, CPython sets this '
+                 'attribute for\n'
+                 'unbound methods that are implemented in C).\n'
+                 '\n'
+                 '\n'
+                 'Invoking Descriptors\n'
+                 '--------------------\n'
+                 '\n'
+                 'In general, a descriptor is an object attribute with '
+                 '“binding\n'
+                 'behavior”, one whose attribute access has been overridden by '
+                 'methods\n'
+                 'in the descriptor protocol:  "__get__()", "__set__()", and\n'
+                 '"__delete__()". If any of those methods are defined for an '
+                 'object, it\n'
+                 'is said to be a descriptor.\n'
+                 '\n'
+                 'The default behavior for attribute access is to get, set, or '
+                 'delete\n'
+                 'the attribute from an object’s dictionary. For instance, '
+                 '"a.x" has a\n'
+                 'lookup chain starting with "a.__dict__[\'x\']", then\n'
+                 '"type(a).__dict__[\'x\']", and continuing through the base '
+                 'classes of\n'
+                 '"type(a)" excluding metaclasses.\n'
+                 '\n'
+                 'However, if the looked-up value is an object defining one of '
+                 'the\n'
+                 'descriptor methods, then Python may override the default '
+                 'behavior and\n'
+                 'invoke the descriptor method instead.  Where this occurs in '
+                 'the\n'
+                 'precedence chain depends on which descriptor methods were '
+                 'defined and\n'
+                 'how they were called.\n'
+                 '\n'
+                 'The starting point for descriptor invocation is a binding, '
+                 '"a.x". How\n'
+                 'the arguments are assembled depends on "a":\n'
+                 '\n'
+                 'Direct Call\n'
+                 '   The simplest and least common call is when user code '
+                 'directly\n'
+                 '   invokes a descriptor method:    "x.__get__(a)".\n'
+                 '\n'
+                 'Instance Binding\n'
+                 '   If binding to an object instance, "a.x" is transformed '
+                 'into the\n'
+                 '   call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n'
+                 '\n'
+                 'Class Binding\n'
+                 '   If binding to a class, "A.x" is transformed into the '
+                 'call:\n'
+                 '   "A.__dict__[\'x\'].__get__(None, A)".\n'
+                 '\n'
+                 'Super Binding\n'
+                 '   If "a" is an instance of "super", then the binding '
+                 '"super(B,\n'
+                 '   obj).m()" searches "obj.__class__.__mro__" for the base '
+                 'class "A"\n'
+                 '   immediately preceding "B" and then invokes the descriptor '
+                 'with the\n'
+                 '   call: "A.__dict__[\'m\'].__get__(obj, obj.__class__)".\n'
+                 '\n'
+                 'For instance bindings, the precedence of descriptor '
+                 'invocation depends\n'
+                 'on the which descriptor methods are defined.  A descriptor '
+                 'can define\n'
+                 'any combination of "__get__()", "__set__()" and '
+                 '"__delete__()".  If it\n'
+                 'does not define "__get__()", then accessing the attribute '
+                 'will return\n'
+                 'the descriptor object itself unless there is a value in the '
+                 'object’s\n'
+                 'instance dictionary.  If the descriptor defines "__set__()" '
+                 'and/or\n'
+                 '"__delete__()", it is a data descriptor; if it defines '
+                 'neither, it is\n'
+                 'a non-data descriptor.  Normally, data descriptors define '
+                 'both\n'
+                 '"__get__()" and "__set__()", while non-data descriptors have '
+                 'just the\n'
+                 '"__get__()" method.  Data descriptors with "__set__()" and '
+                 '"__get__()"\n'
+                 'defined always override a redefinition in an instance '
+                 'dictionary.  In\n'
+                 'contrast, non-data descriptors can be overridden by '
+                 'instances.\n'
+                 '\n'
+                 'Python methods (including "staticmethod()" and '
+                 '"classmethod()") are\n'
+                 'implemented as non-data descriptors.  Accordingly, instances '
+                 'can\n'
+                 'redefine and override methods.  This allows individual '
+                 'instances to\n'
+                 'acquire behaviors that differ from other instances of the '
+                 'same class.\n'
+                 '\n'
+                 'The "property()" function is implemented as a data '
+                 'descriptor.\n'
+                 'Accordingly, instances cannot override the behavior of a '
+                 'property.\n'
+                 '\n'
+                 '\n'
+                 '__slots__\n'
+                 '---------\n'
+                 '\n'
+                 '*__slots__* allow us to explicitly declare data members '
+                 '(like\n'
+                 'properties) and deny the creation of *__dict__* and '
+                 '*__weakref__*\n'
+                 '(unless explicitly declared in *__slots__* or available in a '
+                 'parent.)\n'
+                 '\n'
+                 'The space saved over using *__dict__* can be significant.\n'
+                 '\n'
+                 'object.__slots__\n'
+                 '\n'
+                 '   This class variable can be assigned a string, iterable, '
+                 'or sequence\n'
+                 '   of strings with variable names used by instances.  '
+                 '*__slots__*\n'
+                 '   reserves space for the declared variables and prevents '
+                 'the\n'
+                 '   automatic creation of *__dict__* and *__weakref__* for '
+                 'each\n'
+                 '   instance.\n'
+                 '\n'
+                 '\n'
+                 'Notes on using *__slots__*\n'
+                 '~~~~~~~~~~~~~~~~~~~~~~~~~~\n'
+                 '\n'
+                 '* When inheriting from a class without *__slots__*, the '
+                 '*__dict__*\n'
+                 '  and *__weakref__* attribute of the instances will always '
+                 'be\n'
+                 '  accessible.\n'
+                 '\n'
+                 '* Without a *__dict__* variable, instances cannot be '
+                 'assigned new\n'
+                 '  variables not listed in the *__slots__* definition.  '
+                 'Attempts to\n'
+                 '  assign to an unlisted variable name raises '
+                 '"AttributeError". If\n'
+                 '  dynamic assignment of new variables is desired, then add\n'
+                 '  "\'__dict__\'" to the sequence of strings in the '
+                 '*__slots__*\n'
+                 '  declaration.\n'
+                 '\n'
+                 '* Without a *__weakref__* variable for each instance, '
+                 'classes\n'
+                 '  defining *__slots__* do not support weak references to '
+                 'its\n'
+                 '  instances. If weak reference support is needed, then add\n'
+                 '  "\'__weakref__\'" to the sequence of strings in the '
+                 '*__slots__*\n'
+                 '  declaration.\n'
+                 '\n'
+                 '* *__slots__* are implemented at the class level by '
+                 'creating\n'
+                 '  descriptors (Implementing Descriptors) for each variable '
+                 'name.  As a\n'
+                 '  result, class attributes cannot be used to set default '
+                 'values for\n'
+                 '  instance variables defined by *__slots__*; otherwise, the '
+                 'class\n'
+                 '  attribute would overwrite the descriptor assignment.\n'
+                 '\n'
+                 '* The action of a *__slots__* declaration is not limited to '
+                 'the\n'
+                 '  class where it is defined.  *__slots__* declared in '
+                 'parents are\n'
+                 '  available in child classes. However, child subclasses will '
+                 'get a\n'
+                 '  *__dict__* and *__weakref__* unless they also define '
+                 '*__slots__*\n'
+                 '  (which should only contain names of any *additional* '
+                 'slots).\n'
+                 '\n'
+                 '* If a class defines a slot also defined in a base class, '
+                 'the\n'
+                 '  instance variable defined by the base class slot is '
+                 'inaccessible\n'
+                 '  (except by retrieving its descriptor directly from the '
+                 'base class).\n'
+                 '  This renders the meaning of the program undefined.  In the '
+                 'future, a\n'
+                 '  check may be added to prevent this.\n'
+                 '\n'
+                 '* Nonempty *__slots__* does not work for classes derived '
+                 'from\n'
+                 '  “variable-length” built-in types such as "int", "bytes" '
+                 'and "tuple".\n'
+                 '\n'
+                 '* Any non-string iterable may be assigned to *__slots__*. '
+                 'Mappings\n'
+                 '  may also be used; however, in the future, special meaning '
+                 'may be\n'
+                 '  assigned to the values corresponding to each key.\n'
+                 '\n'
+                 '* *__class__* assignment works only if both classes have the '
+                 'same\n'
+                 '  *__slots__*.\n'
+                 '\n'
+                 '* Multiple inheritance with multiple slotted parent classes '
+                 'can be\n'
+                 '  used, but only one parent is allowed to have attributes '
+                 'created by\n'
+                 '  slots (the other bases must have empty slot layouts) - '
+                 'violations\n'
+                 '  raise "TypeError".\n'
+                 '\n'
+                 '\n'
+                 'Customizing class creation\n'
+                 '==========================\n'
+                 '\n'
+                 'Whenever a class inherits from another class, '
+                 '*__init_subclass__* is\n'
+                 'called on that class. This way, it is possible to write '
+                 'classes which\n'
+                 'change the behavior of subclasses. This is closely related '
+                 'to class\n'
+                 'decorators, but where class decorators only affect the '
+                 'specific class\n'
+                 'they’re applied to, "__init_subclass__" solely applies to '
+                 'future\n'
+                 'subclasses of the class defining the method.\n'
+                 '\n'
+                 'classmethod object.__init_subclass__(cls)\n'
+                 '\n'
+                 '   This method is called whenever the containing class is '
+                 'subclassed.\n'
+                 '   *cls* is then the new subclass. If defined as a normal '
+                 'instance\n'
+                 '   method, this method is implicitly converted to a class '
+                 'method.\n'
+                 '\n'
+                 '   Keyword arguments which are given to a new class are '
+                 'passed to the\n'
+                 '   parent’s class "__init_subclass__". For compatibility '
+                 'with other\n'
+                 '   classes using "__init_subclass__", one should take out '
+                 'the needed\n'
+                 '   keyword arguments and pass the others over to the base '
+                 'class, as\n'
+                 '   in:\n'
+                 '\n'
+                 '      class Philosopher:\n'
+                 '          def __init_subclass__(cls, default_name, '
+                 '**kwargs):\n'
+                 '              super().__init_subclass__(**kwargs)\n'
+                 '              cls.default_name = default_name\n'
+                 '\n'
+                 '      class AustralianPhilosopher(Philosopher, '
+                 'default_name="Bruce"):\n'
+                 '          pass\n'
+                 '\n'
+                 '   The default implementation "object.__init_subclass__" '
+                 'does nothing,\n'
+                 '   but raises an error if it is called with any arguments.\n'
+                 '\n'
+                 '   Note: The metaclass hint "metaclass" is consumed by the '
+                 'rest of\n'
+                 '     the type machinery, and is never passed to '
+                 '"__init_subclass__"\n'
+                 '     implementations. The actual metaclass (rather than the '
+                 'explicit\n'
+                 '     hint) can be accessed as "type(cls)".\n'
+                 '\n'
+                 '   New in version 3.6.\n'
+                 '\n'
+                 '\n'
+                 'Metaclasses\n'
+                 '-----------\n'
+                 '\n'
+                 'By default, classes are constructed using "type()". The '
+                 'class body is\n'
+                 'executed in a new namespace and the class name is bound '
+                 'locally to the\n'
+                 'result of "type(name, bases, namespace)".\n'
+                 '\n'
+                 'The class creation process can be customized by passing the\n'
+                 '"metaclass" keyword argument in the class definition line, '
+                 'or by\n'
+                 'inheriting from an existing class that included such an '
+                 'argument. In\n'
+                 'the following example, both "MyClass" and "MySubclass" are '
+                 'instances\n'
+                 'of "Meta":\n'
+                 '\n'
+                 '   class Meta(type):\n'
+                 '       pass\n'
+                 '\n'
+                 '   class MyClass(metaclass=Meta):\n'
+                 '       pass\n'
+                 '\n'
+                 '   class MySubclass(MyClass):\n'
+                 '       pass\n'
+                 '\n'
+                 'Any other keyword arguments that are specified in the class '
+                 'definition\n'
+                 'are passed through to all metaclass operations described '
+                 'below.\n'
+                 '\n'
+                 'When a class definition is executed, the following steps '
+                 'occur:\n'
+                 '\n'
+                 '* the appropriate metaclass is determined\n'
+                 '\n'
+                 '* the class namespace is prepared\n'
+                 '\n'
+                 '* the class body is executed\n'
+                 '\n'
+                 '* the class object is created\n'
+                 '\n'
+                 '\n'
+                 'Determining the appropriate metaclass\n'
+                 '-------------------------------------\n'
+                 '\n'
+                 'The appropriate metaclass for a class definition is '
+                 'determined as\n'
+                 'follows:\n'
+                 '\n'
+                 '* if no bases and no explicit metaclass are given, then '
+                 '"type()" is\n'
+                 '  used\n'
+                 '\n'
+                 '* if an explicit metaclass is given and it is *not* an '
+                 'instance of\n'
+                 '  "type()", then it is used directly as the metaclass\n'
+                 '\n'
+                 '* if an instance of "type()" is given as the explicit '
+                 'metaclass, or\n'
+                 '  bases are defined, then the most derived metaclass is '
+                 'used\n'
+                 '\n'
+                 'The most derived metaclass is selected from the explicitly '
+                 'specified\n'
+                 'metaclass (if any) and the metaclasses (i.e. "type(cls)") of '
+                 'all\n'
+                 'specified base classes. The most derived metaclass is one '
+                 'which is a\n'
+                 'subtype of *all* of these candidate metaclasses. If none of '
+                 'the\n'
+                 'candidate metaclasses meets that criterion, then the class '
+                 'definition\n'
+                 'will fail with "TypeError".\n'
+                 '\n'
+                 '\n'
+                 'Preparing the class namespace\n'
+                 '-----------------------------\n'
+                 '\n'
+                 'Once the appropriate metaclass has been identified, then the '
+                 'class\n'
+                 'namespace is prepared. If the metaclass has a "__prepare__" '
+                 'attribute,\n'
+                 'it is called as "namespace = metaclass.__prepare__(name, '
+                 'bases,\n'
+                 '**kwds)" (where the additional keyword arguments, if any, '
+                 'come from\n'
+                 'the class definition).\n'
+                 '\n'
+                 'If the metaclass has no "__prepare__" attribute, then the '
+                 'class\n'
+                 'namespace is initialised as an empty ordered mapping.\n'
+                 '\n'
+                 'See also:\n'
+                 '\n'
+                 '  **PEP 3115** - Metaclasses in Python 3000\n'
+                 '     Introduced the "__prepare__" namespace hook\n'
+                 '\n'
+                 '\n'
+                 'Executing the class body\n'
+                 '------------------------\n'
+                 '\n'
+                 'The class body is executed (approximately) as "exec(body, '
+                 'globals(),\n'
+                 'namespace)". The key difference from a normal call to '
+                 '"exec()" is that\n'
+                 'lexical scoping allows the class body (including any '
+                 'methods) to\n'
+                 'reference names from the current and outer scopes when the '
+                 'class\n'
+                 'definition occurs inside a function.\n'
+                 '\n'
+                 'However, even when the class definition occurs inside the '
+                 'function,\n'
+                 'methods defined inside the class still cannot see names '
+                 'defined at the\n'
+                 'class scope. Class variables must be accessed through the '
+                 'first\n'
+                 'parameter of instance or class methods, or through the '
+                 'implicit\n'
+                 'lexically scoped "__class__" reference described in the next '
+                 'section.\n'
+                 '\n'
+                 '\n'
+                 'Creating the class object\n'
+                 '-------------------------\n'
+                 '\n'
+                 'Once the class namespace has been populated by executing the '
+                 'class\n'
+                 'body, the class object is created by calling '
+                 '"metaclass(name, bases,\n'
+                 'namespace, **kwds)" (the additional keywords passed here are '
+                 'the same\n'
+                 'as those passed to "__prepare__").\n'
+                 '\n'
+                 'This class object is the one that will be referenced by the '
+                 'zero-\n'
+                 'argument form of "super()". "__class__" is an implicit '
+                 'closure\n'
+                 'reference created by the compiler if any methods in a class '
+                 'body refer\n'
+                 'to either "__class__" or "super". This allows the zero '
+                 'argument form\n'
+                 'of "super()" to correctly identify the class being defined '
+                 'based on\n'
+                 'lexical scoping, while the class or instance that was used '
+                 'to make the\n'
+                 'current call is identified based on the first argument '
+                 'passed to the\n'
+                 'method.\n'
+                 '\n'
+                 '**CPython implementation detail:** In CPython 3.6 and later, '
+                 'the\n'
+                 '"__class__" cell is passed to the metaclass as a '
+                 '"__classcell__" entry\n'
+                 'in the class namespace. If present, this must be propagated '
+                 'up to the\n'
+                 '"type.__new__" call in order for the class to be '
+                 'initialised\n'
+                 'correctly. Failing to do so will result in a '
+                 '"DeprecationWarning" in\n'
+                 'Python 3.6, and a "RuntimeError" in Python 3.8.\n'
+                 '\n'
+                 'When using the default metaclass "type", or any metaclass '
+                 'that\n'
+                 'ultimately calls "type.__new__", the following additional\n'
+                 'customisation steps are invoked after creating the class '
+                 'object:\n'
+                 '\n'
+                 '* first, "type.__new__" collects all of the descriptors in '
+                 'the class\n'
+                 '  namespace that define a "__set_name__()" method;\n'
+                 '\n'
+                 '* second, all of these "__set_name__" methods are called '
+                 'with the\n'
+                 '  class being defined and the assigned name of that '
+                 'particular\n'
+                 '  descriptor; and\n'
+                 '\n'
+                 '* finally, the "__init_subclass__()" hook is called on the '
+                 'immediate\n'
+                 '  parent of the new class in its method resolution order.\n'
+                 '\n'
+                 'After the class object is created, it is passed to the '
+                 'class\n'
+                 'decorators included in the class definition (if any) and the '
+                 'resulting\n'
+                 'object is bound in the local namespace as the defined '
+                 'class.\n'
+                 '\n'
+                 'When a new class is created by "type.__new__", the object '
+                 'provided as\n'
+                 'the namespace parameter is copied to a new ordered mapping '
+                 'and the\n'
+                 'original object is discarded. The new copy is wrapped in a '
+                 'read-only\n'
+                 'proxy, which becomes the "__dict__" attribute of the class '
+                 'object.\n'
+                 '\n'
+                 'See also:\n'
+                 '\n'
+                 '  **PEP 3135** - New super\n'
+                 '     Describes the implicit "__class__" closure reference\n'
+                 '\n'
+                 '\n'
+                 'Uses for metaclasses\n'
+                 '--------------------\n'
+                 '\n'
+                 'The potential uses for metaclasses are boundless. Some ideas '
+                 'that have\n'
+                 'been explored include enum, logging, interface checking, '
+                 'automatic\n'
+                 'delegation, automatic property creation, proxies, '
+                 'frameworks, and\n'
+                 'automatic resource locking/synchronization.\n'
+                 '\n'
+                 '\n'
+                 'Customizing instance and subclass checks\n'
+                 '========================================\n'
+                 '\n'
+                 'The following methods are used to override the default '
+                 'behavior of the\n'
+                 '"isinstance()" and "issubclass()" built-in functions.\n'
+                 '\n'
+                 'In particular, the metaclass "abc.ABCMeta" implements these '
+                 'methods in\n'
+                 'order to allow the addition of Abstract Base Classes (ABCs) '
+                 'as\n'
+                 '“virtual base classes” to any class or type (including '
+                 'built-in\n'
+                 'types), including other ABCs.\n'
+                 '\n'
+                 'class.__instancecheck__(self, instance)\n'
+                 '\n'
+                 '   Return true if *instance* should be considered a (direct '
+                 'or\n'
+                 '   indirect) instance of *class*. If defined, called to '
+                 'implement\n'
+                 '   "isinstance(instance, class)".\n'
+                 '\n'
+                 'class.__subclasscheck__(self, subclass)\n'
+                 '\n'
+                 '   Return true if *subclass* should be considered a (direct '
+                 'or\n'
+                 '   indirect) subclass of *class*.  If defined, called to '
+                 'implement\n'
+                 '   "issubclass(subclass, class)".\n'
+                 '\n'
+                 'Note that these methods are looked up on the type '
+                 '(metaclass) of a\n'
+                 'class.  They cannot be defined as class methods in the '
+                 'actual class.\n'
+                 'This is consistent with the lookup of special methods that '
+                 'are called\n'
+                 'on instances, only in this case the instance is itself a '
+                 'class.\n'
+                 '\n'
+                 'See also:\n'
+                 '\n'
+                 '  **PEP 3119** - Introducing Abstract Base Classes\n'
+                 '     Includes the specification for customizing '
+                 '"isinstance()" and\n'
+                 '     "issubclass()" behavior through "__instancecheck__()" '
+                 'and\n'
+                 '     "__subclasscheck__()", with motivation for this '
+                 'functionality in\n'
+                 '     the context of adding Abstract Base Classes (see the '
+                 '"abc"\n'
+                 '     module) to the language.\n'
+                 '\n'
+                 '\n'
+                 'Emulating callable objects\n'
+                 '==========================\n'
+                 '\n'
+                 'object.__call__(self[, args...])\n'
+                 '\n'
+                 '   Called when the instance is “called” as a function; if '
+                 'this method\n'
+                 '   is defined, "x(arg1, arg2, ...)" is a shorthand for\n'
+                 '   "x.__call__(arg1, arg2, ...)".\n'
+                 '\n'
+                 '\n'
+                 'Emulating container types\n'
+                 '=========================\n'
+                 '\n'
+                 'The following methods can be defined to implement container '
+                 'objects.\n'
+                 'Containers usually are sequences (such as lists or tuples) '
+                 'or mappings\n'
+                 '(like dictionaries), but can represent other containers as '
+                 'well.  The\n'
+                 'first set of methods is used either to emulate a sequence or '
+                 'to\n'
+                 'emulate a mapping; the difference is that for a sequence, '
+                 'the\n'
+                 'allowable keys should be the integers *k* for which "0 <= k '
+                 '< N" where\n'
+                 '*N* is the length of the sequence, or slice objects, which '
+                 'define a\n'
+                 'range of items.  It is also recommended that mappings '
+                 'provide the\n'
+                 'methods "keys()", "values()", "items()", "get()", '
+                 '"clear()",\n'
+                 '"setdefault()", "pop()", "popitem()", "copy()", and '
+                 '"update()"\n'
+                 'behaving similar to those for Python’s standard dictionary '
+                 'objects.\n'
+                 'The "collections" module provides a "MutableMapping" '
+                 'abstract base\n'
+                 'class to help create those methods from a base set of '
+                 '"__getitem__()",\n'
+                 '"__setitem__()", "__delitem__()", and "keys()". Mutable '
+                 'sequences\n'
+                 'should provide methods "append()", "count()", "index()", '
+                 '"extend()",\n'
+                 '"insert()", "pop()", "remove()", "reverse()" and "sort()", '
+                 'like Python\n'
+                 'standard list objects.  Finally, sequence types should '
+                 'implement\n'
+                 'addition (meaning concatenation) and multiplication '
+                 '(meaning\n'
+                 'repetition) by defining the methods "__add__()", '
+                 '"__radd__()",\n'
+                 '"__iadd__()", "__mul__()", "__rmul__()" and "__imul__()" '
+                 'described\n'
+                 'below; they should not define other numerical operators.  It '
+                 'is\n'
+                 'recommended that both mappings and sequences implement the\n'
+                 '"__contains__()" method to allow efficient use of the "in" '
+                 'operator;\n'
+                 'for mappings, "in" should search the mapping’s keys; for '
+                 'sequences, it\n'
+                 'should search through the values.  It is further recommended '
+                 'that both\n'
+                 'mappings and sequences implement the "__iter__()" method to '
+                 'allow\n'
+                 'efficient iteration through the container; for mappings, '
+                 '"__iter__()"\n'
+                 'should be the same as "keys()"; for sequences, it should '
+                 'iterate\n'
+                 'through the values.\n'
+                 '\n'
+                 'object.__len__(self)\n'
+                 '\n'
+                 '   Called to implement the built-in function "len()".  '
+                 'Should return\n'
+                 '   the length of the object, an integer ">=" 0.  Also, an '
+                 'object that\n'
+                 '   doesn’t define a "__bool__()" method and whose '
+                 '"__len__()" method\n'
+                 '   returns zero is considered to be false in a Boolean '
+                 'context.\n'
+                 '\n'
+                 '   **CPython implementation detail:** In CPython, the length '
+                 'is\n'
+                 '   required to be at most "sys.maxsize". If the length is '
+                 'larger than\n'
+                 '   "sys.maxsize" some features (such as "len()") may raise\n'
+                 '   "OverflowError".  To prevent raising "OverflowError" by '
+                 'truth value\n'
+                 '   testing, an object must define a "__bool__()" method.\n'
+                 '\n'
+                 'object.__length_hint__(self)\n'
+                 '\n'
+                 '   Called to implement "operator.length_hint()". Should '
+                 'return an\n'
+                 '   estimated length for the object (which may be greater or '
+                 'less than\n'
+                 '   the actual length). The length must be an integer ">=" 0. '
+                 'This\n'
+                 '   method is purely an optimization and is never required '
+                 'for\n'
+                 '   correctness.\n'
+                 '\n'
+                 '   New in version 3.4.\n'
+                 '\n'
+                 'Note: Slicing is done exclusively with the following three '
+                 'methods.\n'
+                 '  A call like\n'
+                 '\n'
+                 '     a[1:2] = b\n'
+                 '\n'
+                 '  is translated to\n'
+                 '\n'
+                 '     a[slice(1, 2, None)] = b\n'
+                 '\n'
+                 '  and so forth.  Missing slice items are always filled in '
+                 'with "None".\n'
+                 '\n'
+                 'object.__getitem__(self, key)\n'
+                 '\n'
+                 '   Called to implement evaluation of "self[key]". For '
+                 'sequence types,\n'
+                 '   the accepted keys should be integers and slice objects.  '
+                 'Note that\n'
+                 '   the special interpretation of negative indexes (if the '
+                 'class wishes\n'
+                 '   to emulate a sequence type) is up to the "__getitem__()" '
+                 'method. If\n'
+                 '   *key* is of an inappropriate type, "TypeError" may be '
+                 'raised; if of\n'
+                 '   a value outside the set of indexes for the sequence '
+                 '(after any\n'
+                 '   special interpretation of negative values), "IndexError" '
+                 'should be\n'
+                 '   raised. For mapping types, if *key* is missing (not in '
+                 'the\n'
+                 '   container), "KeyError" should be raised.\n'
+                 '\n'
+                 '   Note: "for" loops expect that an "IndexError" will be '
+                 'raised for\n'
+                 '     illegal indexes to allow proper detection of the end of '
+                 'the\n'
+                 '     sequence.\n'
+                 '\n'
+                 'object.__setitem__(self, key, value)\n'
+                 '\n'
+                 '   Called to implement assignment to "self[key]".  Same note '
+                 'as for\n'
+                 '   "__getitem__()".  This should only be implemented for '
+                 'mappings if\n'
+                 '   the objects support changes to the values for keys, or if '
+                 'new keys\n'
+                 '   can be added, or for sequences if elements can be '
+                 'replaced.  The\n'
+                 '   same exceptions should be raised for improper *key* '
+                 'values as for\n'
+                 '   the "__getitem__()" method.\n'
+                 '\n'
+                 'object.__delitem__(self, key)\n'
+                 '\n'
+                 '   Called to implement deletion of "self[key]".  Same note '
+                 'as for\n'
+                 '   "__getitem__()".  This should only be implemented for '
+                 'mappings if\n'
+                 '   the objects support removal of keys, or for sequences if '
+                 'elements\n'
+                 '   can be removed from the sequence.  The same exceptions '
+                 'should be\n'
+                 '   raised for improper *key* values as for the '
+                 '"__getitem__()" method.\n'
+                 '\n'
+                 'object.__missing__(self, key)\n'
+                 '\n'
+                 '   Called by "dict"."__getitem__()" to implement "self[key]" '
+                 'for dict\n'
+                 '   subclasses when key is not in the dictionary.\n'
+                 '\n'
+                 'object.__iter__(self)\n'
+                 '\n'
+                 '   This method is called when an iterator is required for a '
+                 'container.\n'
+                 '   This method should return a new iterator object that can '
+                 'iterate\n'
+                 '   over all the objects in the container.  For mappings, it '
+                 'should\n'
+                 '   iterate over the keys of the container.\n'
+                 '\n'
+                 '   Iterator objects also need to implement this method; they '
+                 'are\n'
+                 '   required to return themselves.  For more information on '
+                 'iterator\n'
+                 '   objects, see Iterator Types.\n'
+                 '\n'
+                 'object.__reversed__(self)\n'
+                 '\n'
+                 '   Called (if present) by the "reversed()" built-in to '
+                 'implement\n'
+                 '   reverse iteration.  It should return a new iterator '
+                 'object that\n'
+                 '   iterates over all the objects in the container in reverse '
+                 'order.\n'
+                 '\n'
+                 '   If the "__reversed__()" method is not provided, the '
+                 '"reversed()"\n'
+                 '   built-in will fall back to using the sequence protocol '
+                 '("__len__()"\n'
+                 '   and "__getitem__()").  Objects that support the sequence '
+                 'protocol\n'
+                 '   should only provide "__reversed__()" if they can provide '
+                 'an\n'
+                 '   implementation that is more efficient than the one '
+                 'provided by\n'
+                 '   "reversed()".\n'
+                 '\n'
+                 'The membership test operators ("in" and "not in") are '
+                 'normally\n'
+                 'implemented as an iteration through a sequence.  However, '
+                 'container\n'
+                 'objects can supply the following special method with a more '
+                 'efficient\n'
+                 'implementation, which also does not require the object be a '
+                 'sequence.\n'
+                 '\n'
+                 'object.__contains__(self, item)\n'
+                 '\n'
+                 '   Called to implement membership test operators.  Should '
+                 'return true\n'
+                 '   if *item* is in *self*, false otherwise.  For mapping '
+                 'objects, this\n'
+                 '   should consider the keys of the mapping rather than the '
+                 'values or\n'
+                 '   the key-item pairs.\n'
+                 '\n'
+                 '   For objects that don’t define "__contains__()", the '
+                 'membership test\n'
+                 '   first tries iteration via "__iter__()", then the old '
+                 'sequence\n'
+                 '   iteration protocol via "__getitem__()", see this section '
+                 'in the\n'
+                 '   language reference.\n'
+                 '\n'
+                 '\n'
+                 'Emulating numeric types\n'
+                 '=======================\n'
+                 '\n'
+                 'The following methods can be defined to emulate numeric '
+                 'objects.\n'
+                 'Methods corresponding to operations that are not supported '
+                 'by the\n'
+                 'particular kind of number implemented (e.g., bitwise '
+                 'operations for\n'
+                 'non-integral numbers) should be left undefined.\n'
+                 '\n'
+                 'object.__add__(self, other)\n'
+                 'object.__sub__(self, other)\n'
+                 'object.__mul__(self, other)\n'
+                 'object.__matmul__(self, other)\n'
+                 'object.__truediv__(self, other)\n'
+                 'object.__floordiv__(self, other)\n'
+                 'object.__mod__(self, other)\n'
+                 'object.__divmod__(self, other)\n'
+                 'object.__pow__(self, other[, modulo])\n'
+                 'object.__lshift__(self, other)\n'
+                 'object.__rshift__(self, other)\n'
+                 'object.__and__(self, other)\n'
+                 'object.__xor__(self, other)\n'
+                 'object.__or__(self, other)\n'
+                 '\n'
+                 '   These methods are called to implement the binary '
+                 'arithmetic\n'
+                 '   operations ("+", "-", "*", "@", "/", "//", "%", '
+                 '"divmod()",\n'
+                 '   "pow()", "**", "<<", ">>", "&", "^", "|").  For instance, '
+                 'to\n'
+                 '   evaluate the expression "x + y", where *x* is an instance '
+                 'of a\n'
+                 '   class that has an "__add__()" method, "x.__add__(y)" is '
+                 'called.\n'
+                 '   The "__divmod__()" method should be the equivalent to '
+                 'using\n'
+                 '   "__floordiv__()" and "__mod__()"; it should not be '
+                 'related to\n'
+                 '   "__truediv__()".  Note that "__pow__()" should be defined '
+                 'to accept\n'
+                 '   an optional third argument if the ternary version of the '
+                 'built-in\n'
+                 '   "pow()" function is to be supported.\n'
+                 '\n'
+                 '   If one of those methods does not support the operation '
+                 'with the\n'
+                 '   supplied arguments, it should return "NotImplemented".\n'
+                 '\n'
+                 'object.__radd__(self, other)\n'
+                 'object.__rsub__(self, other)\n'
+                 'object.__rmul__(self, other)\n'
+                 'object.__rmatmul__(self, other)\n'
+                 'object.__rtruediv__(self, other)\n'
+                 'object.__rfloordiv__(self, other)\n'
+                 'object.__rmod__(self, other)\n'
+                 'object.__rdivmod__(self, other)\n'
+                 'object.__rpow__(self, other)\n'
+                 'object.__rlshift__(self, other)\n'
+                 'object.__rrshift__(self, other)\n'
+                 'object.__rand__(self, other)\n'
+                 'object.__rxor__(self, other)\n'
+                 'object.__ror__(self, other)\n'
+                 '\n'
+                 '   These methods are called to implement the binary '
+                 'arithmetic\n'
+                 '   operations ("+", "-", "*", "@", "/", "//", "%", '
+                 '"divmod()",\n'
+                 '   "pow()", "**", "<<", ">>", "&", "^", "|") with reflected '
+                 '(swapped)\n'
+                 '   operands.  These functions are only called if the left '
+                 'operand does\n'
+                 '   not support the corresponding operation [3] and the '
+                 'operands are of\n'
+                 '   different types. [4] For instance, to evaluate the '
+                 'expression "x -\n'
+                 '   y", where *y* is an instance of a class that has an '
+                 '"__rsub__()"\n'
+                 '   method, "y.__rsub__(x)" is called if "x.__sub__(y)" '
+                 'returns\n'
+                 '   *NotImplemented*.\n'
+                 '\n'
+                 '   Note that ternary "pow()" will not try calling '
+                 '"__rpow__()" (the\n'
+                 '   coercion rules would become too complicated).\n'
+                 '\n'
+                 '   Note: If the right operand’s type is a subclass of the '
+                 'left\n'
+                 '     operand’s type and that subclass provides the reflected '
+                 'method\n'
+                 '     for the operation, this method will be called before '
+                 'the left\n'
+                 '     operand’s non-reflected method.  This behavior allows '
+                 'subclasses\n'
+                 '     to override their ancestors’ operations.\n'
+                 '\n'
+                 'object.__iadd__(self, other)\n'
+                 'object.__isub__(self, other)\n'
+                 'object.__imul__(self, other)\n'
+                 'object.__imatmul__(self, other)\n'
+                 'object.__itruediv__(self, other)\n'
+                 'object.__ifloordiv__(self, other)\n'
+                 'object.__imod__(self, other)\n'
+                 'object.__ipow__(self, other[, modulo])\n'
+                 'object.__ilshift__(self, other)\n'
+                 'object.__irshift__(self, other)\n'
+                 'object.__iand__(self, other)\n'
+                 'object.__ixor__(self, other)\n'
+                 'object.__ior__(self, other)\n'
+                 '\n'
+                 '   These methods are called to implement the augmented '
+                 'arithmetic\n'
+                 '   assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", '
+                 '"**=",\n'
+                 '   "<<=", ">>=", "&=", "^=", "|=").  These methods should '
+                 'attempt to\n'
+                 '   do the operation in-place (modifying *self*) and return '
+                 'the result\n'
+                 '   (which could be, but does not have to be, *self*).  If a '
+                 'specific\n'
+                 '   method is not defined, the augmented assignment falls '
+                 'back to the\n'
+                 '   normal methods.  For instance, if *x* is an instance of a '
+                 'class\n'
+                 '   with an "__iadd__()" method, "x += y" is equivalent to "x '
+                 '=\n'
+                 '   x.__iadd__(y)" . Otherwise, "x.__add__(y)" and '
+                 '"y.__radd__(x)" are\n'
+                 '   considered, as with the evaluation of "x + y". In '
+                 'certain\n'
+                 '   situations, augmented assignment can result in unexpected '
+                 'errors\n'
+                 '   (see Why does a_tuple[i] += [‘item’] raise an exception '
+                 'when the\n'
+                 '   addition works?), but this behavior is in fact part of '
+                 'the data\n'
+                 '   model.\n'
+                 '\n'
+                 'object.__neg__(self)\n'
+                 'object.__pos__(self)\n'
+                 'object.__abs__(self)\n'
+                 'object.__invert__(self)\n'
+                 '\n'
+                 '   Called to implement the unary arithmetic operations ("-", '
+                 '"+",\n'
+                 '   "abs()" and "~").\n'
+                 '\n'
+                 'object.__complex__(self)\n'
+                 'object.__int__(self)\n'
+                 'object.__float__(self)\n'
+                 '\n'
+                 '   Called to implement the built-in functions "complex()", '
+                 '"int()" and\n'
+                 '   "float()".  Should return a value of the appropriate '
+                 'type.\n'
+                 '\n'
+                 'object.__index__(self)\n'
+                 '\n'
+                 '   Called to implement "operator.index()", and whenever '
+                 'Python needs\n'
+                 '   to losslessly convert the numeric object to an integer '
+                 'object (such\n'
+                 '   as in slicing, or in the built-in "bin()", "hex()" and '
+                 '"oct()"\n'
+                 '   functions). Presence of this method indicates that the '
+                 'numeric\n'
+                 '   object is an integer type.  Must return an integer.\n'
+                 '\n'
+                 '   Note: In order to have a coherent integer type class, '
+                 'when\n'
+                 '     "__index__()" is defined "__int__()" should also be '
+                 'defined, and\n'
+                 '     both should return the same value.\n'
+                 '\n'
+                 'object.__round__(self[, ndigits])\n'
+                 'object.__trunc__(self)\n'
+                 'object.__floor__(self)\n'
+                 'object.__ceil__(self)\n'
+                 '\n'
+                 '   Called to implement the built-in function "round()" and '
+                 '"math"\n'
+                 '   functions "trunc()", "floor()" and "ceil()". Unless '
+                 '*ndigits* is\n'
+                 '   passed to "__round__()" all these methods should return '
+                 'the value\n'
+                 '   of the object truncated to an "Integral" (typically an '
+                 '"int").\n'
+                 '\n'
+                 '   If "__int__()" is not defined then the built-in function '
+                 '"int()"\n'
+                 '   falls back to "__trunc__()".\n'
+                 '\n'
+                 '\n'
+                 'With Statement Context Managers\n'
+                 '===============================\n'
+                 '\n'
+                 'A *context manager* is an object that defines the runtime '
+                 'context to\n'
+                 'be established when executing a "with" statement. The '
+                 'context manager\n'
+                 'handles the entry into, and the exit from, the desired '
+                 'runtime context\n'
+                 'for the execution of the block of code.  Context managers '
+                 'are normally\n'
+                 'invoked using the "with" statement (described in section The '
+                 'with\n'
+                 'statement), but can also be used by directly invoking their '
+                 'methods.\n'
+                 '\n'
+                 'Typical uses of context managers include saving and '
+                 'restoring various\n'
+                 'kinds of global state, locking and unlocking resources, '
+                 'closing opened\n'
+                 'files, etc.\n'
+                 '\n'
+                 'For more information on context managers, see Context '
+                 'Manager Types.\n'
+                 '\n'
+                 'object.__enter__(self)\n'
+                 '\n'
+                 '   Enter the runtime context related to this object. The '
+                 '"with"\n'
+                 '   statement will bind this method’s return value to the '
+                 'target(s)\n'
+                 '   specified in the "as" clause of the statement, if any.\n'
+                 '\n'
+                 'object.__exit__(self, exc_type, exc_value, traceback)\n'
+                 '\n'
+                 '   Exit the runtime context related to this object. The '
+                 'parameters\n'
+                 '   describe the exception that caused the context to be '
+                 'exited. If the\n'
+                 '   context was exited without an exception, all three '
+                 'arguments will\n'
+                 '   be "None".\n'
+                 '\n'
+                 '   If an exception is supplied, and the method wishes to '
+                 'suppress the\n'
+                 '   exception (i.e., prevent it from being propagated), it '
+                 'should\n'
+                 '   return a true value. Otherwise, the exception will be '
+                 'processed\n'
+                 '   normally upon exit from this method.\n'
+                 '\n'
+                 '   Note that "__exit__()" methods should not reraise the '
+                 'passed-in\n'
+                 '   exception; this is the caller’s responsibility.\n'
+                 '\n'
+                 'See also:\n'
+                 '\n'
+                 '  **PEP 343** - The “with” statement\n'
+                 '     The specification, background, and examples for the '
+                 'Python "with"\n'
+                 '     statement.\n'
+                 '\n'
+                 '\n'
+                 'Special method lookup\n'
+                 '=====================\n'
+                 '\n'
+                 'For custom classes, implicit invocations of special methods '
+                 'are only\n'
+                 'guaranteed to work correctly if defined on an object’s type, '
+                 'not in\n'
+                 'the object’s instance dictionary.  That behaviour is the '
+                 'reason why\n'
+                 'the following code raises an exception:\n'
+                 '\n'
+                 '   >>> class C:\n'
+                 '   ...     pass\n'
+                 '   ...\n'
+                 '   >>> c = C()\n'
+                 '   >>> c.__len__ = lambda: 5\n'
+                 '   >>> len(c)\n'
+                 '   Traceback (most recent call last):\n'
+                 '     File "<stdin>", line 1, in <module>\n'
+                 "   TypeError: object of type 'C' has no len()\n"
+                 '\n'
+                 'The rationale behind this behaviour lies with a number of '
+                 'special\n'
+                 'methods such as "__hash__()" and "__repr__()" that are '
+                 'implemented by\n'
+                 'all objects, including type objects. If the implicit lookup '
+                 'of these\n'
+                 'methods used the conventional lookup process, they would '
+                 'fail when\n'
+                 'invoked on the type object itself:\n'
+                 '\n'
+                 '   >>> 1 .__hash__() == hash(1)\n'
+                 '   True\n'
+                 '   >>> int.__hash__() == hash(int)\n'
+                 '   Traceback (most recent call last):\n'
+                 '     File "<stdin>", line 1, in <module>\n'
+                 "   TypeError: descriptor '__hash__' of 'int' object needs an "
+                 'argument\n'
+                 '\n'
+                 'Incorrectly attempting to invoke an unbound method of a '
+                 'class in this\n'
+                 'way is sometimes referred to as ‘metaclass confusion’, and '
+                 'is avoided\n'
+                 'by bypassing the instance when looking up special methods:\n'
+                 '\n'
+                 '   >>> type(1).__hash__(1) == hash(1)\n'
+                 '   True\n'
+                 '   >>> type(int).__hash__(int) == hash(int)\n'
+                 '   True\n'
+                 '\n'
+                 'In addition to bypassing any instance attributes in the '
+                 'interest of\n'
+                 'correctness, implicit special method lookup generally also '
+                 'bypasses\n'
+                 'the "__getattribute__()" method even of the object’s '
+                 'metaclass:\n'
+                 '\n'
+                 '   >>> class Meta(type):\n'
+                 '   ...     def __getattribute__(*args):\n'
+                 '   ...         print("Metaclass getattribute invoked")\n'
+                 '   ...         return type.__getattribute__(*args)\n'
+                 '   ...\n'
+                 '   >>> class C(object, metaclass=Meta):\n'
+                 '   ...     def __len__(self):\n'
+                 '   ...         return 10\n'
+                 '   ...     def __getattribute__(*args):\n'
+                 '   ...         print("Class getattribute invoked")\n'
+                 '   ...         return object.__getattribute__(*args)\n'
+                 '   ...\n'
+                 '   >>> c = C()\n'
+                 '   >>> c.__len__()                 # Explicit lookup via '
+                 'instance\n'
+                 '   Class getattribute invoked\n'
+                 '   10\n'
+                 '   >>> type(c).__len__(c)          # Explicit lookup via '
+                 'type\n'
+                 '   Metaclass getattribute invoked\n'
+                 '   10\n'
+                 '   >>> len(c)                      # Implicit lookup\n'
+                 '   10\n'
+                 '\n'
+                 'Bypassing the "__getattribute__()" machinery in this fashion '
+                 'provides\n'
+                 'significant scope for speed optimisations within the '
+                 'interpreter, at\n'
+                 'the cost of some flexibility in the handling of special '
+                 'methods (the\n'
+                 'special method *must* be set on the class object itself in '
+                 'order to be\n'
+                 'consistently invoked by the interpreter).\n',
+ 'string-methods': 'String Methods\n'
+                   '**************\n'
+                   '\n'
+                   'Strings implement all of the common sequence operations, '
+                   'along with\n'
+                   'the additional methods described below.\n'
+                   '\n'
+                   'Strings also support two styles of string formatting, one '
+                   'providing a\n'
+                   'large degree of flexibility and customization (see '
+                   '"str.format()",\n'
+                   'Format String Syntax and Custom String Formatting) and the '
+                   'other based\n'
+                   'on C "printf" style formatting that handles a narrower '
+                   'range of types\n'
+                   'and is slightly harder to use correctly, but is often '
+                   'faster for the\n'
+                   'cases it can handle (printf-style String Formatting).\n'
+                   '\n'
+                   'The Text Processing Services section of the standard '
+                   'library covers a\n'
+                   'number of other modules that provide various text related '
+                   'utilities\n'
+                   '(including regular expression support in the "re" '
+                   'module).\n'
+                   '\n'
+                   'str.capitalize()\n'
+                   '\n'
+                   '   Return a copy of the string with its first character '
+                   'capitalized\n'
+                   '   and the rest lowercased.\n'
+                   '\n'
+                   'str.casefold()\n'
+                   '\n'
+                   '   Return a casefolded copy of the string. Casefolded '
+                   'strings may be\n'
+                   '   used for caseless matching.\n'
+                   '\n'
+                   '   Casefolding is similar to lowercasing but more '
+                   'aggressive because\n'
+                   '   it is intended to remove all case distinctions in a '
+                   'string. For\n'
+                   '   example, the German lowercase letter "\'ß\'" is '
+                   'equivalent to ""ss"".\n'
+                   '   Since it is already lowercase, "lower()" would do '
+                   'nothing to "\'ß\'";\n'
+                   '   "casefold()" converts it to ""ss"".\n'
+                   '\n'
+                   '   The casefolding algorithm is described in section 3.13 '
+                   'of the\n'
+                   '   Unicode Standard.\n'
+                   '\n'
+                   '   New in version 3.3.\n'
+                   '\n'
+                   'str.center(width[, fillchar])\n'
+                   '\n'
+                   '   Return centered in a string of length *width*. Padding '
+                   'is done\n'
+                   '   using the specified *fillchar* (default is an ASCII '
+                   'space). The\n'
+                   '   original string is returned if *width* is less than or '
+                   'equal to\n'
+                   '   "len(s)".\n'
+                   '\n'
+                   'str.count(sub[, start[, end]])\n'
+                   '\n'
+                   '   Return the number of non-overlapping occurrences of '
+                   'substring *sub*\n'
+                   '   in the range [*start*, *end*].  Optional arguments '
+                   '*start* and\n'
+                   '   *end* are interpreted as in slice notation.\n'
+                   '\n'
+                   'str.encode(encoding="utf-8", errors="strict")\n'
+                   '\n'
+                   '   Return an encoded version of the string as a bytes '
+                   'object. Default\n'
+                   '   encoding is "\'utf-8\'". *errors* may be given to set a '
+                   'different\n'
+                   '   error handling scheme. The default for *errors* is '
+                   '"\'strict\'",\n'
+                   '   meaning that encoding errors raise a "UnicodeError". '
+                   'Other possible\n'
+                   '   values are "\'ignore\'", "\'replace\'", '
+                   '"\'xmlcharrefreplace\'",\n'
+                   '   "\'backslashreplace\'" and any other name registered '
+                   'via\n'
+                   '   "codecs.register_error()", see section Error Handlers. '
+                   'For a list\n'
+                   '   of possible encodings, see section Standard Encodings.\n'
+                   '\n'
+                   '   Changed in version 3.1: Support for keyword arguments '
+                   'added.\n'
+                   '\n'
+                   'str.endswith(suffix[, start[, end]])\n'
+                   '\n'
+                   '   Return "True" if the string ends with the specified '
+                   '*suffix*,\n'
+                   '   otherwise return "False".  *suffix* can also be a tuple '
+                   'of suffixes\n'
+                   '   to look for.  With optional *start*, test beginning at '
+                   'that\n'
+                   '   position.  With optional *end*, stop comparing at that '
+                   'position.\n'
+                   '\n'
+                   'str.expandtabs(tabsize=8)\n'
+                   '\n'
+                   '   Return a copy of the string where all tab characters '
+                   'are replaced\n'
+                   '   by one or more spaces, depending on the current column '
+                   'and the\n'
+                   '   given tab size.  Tab positions occur every *tabsize* '
+                   'characters\n'
+                   '   (default is 8, giving tab positions at columns 0, 8, 16 '
+                   'and so on).\n'
+                   '   To expand the string, the current column is set to zero '
+                   'and the\n'
+                   '   string is examined character by character.  If the '
+                   'character is a\n'
+                   '   tab ("\\t"), one or more space characters are inserted '
+                   'in the result\n'
+                   '   until the current column is equal to the next tab '
+                   'position. (The\n'
+                   '   tab character itself is not copied.)  If the character '
+                   'is a newline\n'
+                   '   ("\\n") or return ("\\r"), it is copied and the current '
+                   'column is\n'
+                   '   reset to zero.  Any other character is copied unchanged '
+                   'and the\n'
+                   '   current column is incremented by one regardless of how '
+                   'the\n'
+                   '   character is represented when printed.\n'
+                   '\n'
+                   "   >>> '01\\t012\\t0123\\t01234'.expandtabs()\n"
+                   "   '01      012     0123    01234'\n"
+                   "   >>> '01\\t012\\t0123\\t01234'.expandtabs(4)\n"
+                   "   '01  012 0123    01234'\n"
+                   '\n'
+                   'str.find(sub[, start[, end]])\n'
+                   '\n'
+                   '   Return the lowest index in the string where substring '
+                   '*sub* is\n'
+                   '   found within the slice "s[start:end]".  Optional '
+                   'arguments *start*\n'
+                   '   and *end* are interpreted as in slice notation.  Return '
+                   '"-1" if\n'
+                   '   *sub* is not found.\n'
+                   '\n'
+                   '   Note: The "find()" method should be used only if you '
+                   'need to know\n'
+                   '     the position of *sub*.  To check if *sub* is a '
+                   'substring or not,\n'
+                   '     use the "in" operator:\n'
+                   '\n'
+                   "        >>> 'Py' in 'Python'\n"
+                   '        True\n'
+                   '\n'
+                   'str.format(*args, **kwargs)\n'
+                   '\n'
+                   '   Perform a string formatting operation.  The string on '
+                   'which this\n'
+                   '   method is called can contain literal text or '
+                   'replacement fields\n'
+                   '   delimited by braces "{}".  Each replacement field '
+                   'contains either\n'
+                   '   the numeric index of a positional argument, or the name '
+                   'of a\n'
+                   '   keyword argument.  Returns a copy of the string where '
+                   'each\n'
+                   '   replacement field is replaced with the string value of '
+                   'the\n'
+                   '   corresponding argument.\n'
+                   '\n'
+                   '   >>> "The sum of 1 + 2 is {0}".format(1+2)\n'
+                   "   'The sum of 1 + 2 is 3'\n"
+                   '\n'
+                   '   See Format String Syntax for a description of the '
+                   'various\n'
+                   '   formatting options that can be specified in format '
+                   'strings.\n'
+                   '\n'
+                   '   Note: When formatting a number ("int", "float", '
+                   '"complex",\n'
+                   '     "decimal.Decimal" and subclasses) with the "n" type '
+                   '(ex:\n'
+                   '     "\'{:n}\'.format(1234)"), the function temporarily '
+                   'sets the\n'
+                   '     "LC_CTYPE" locale to the "LC_NUMERIC" locale to '
+                   'decode\n'
+                   '     "decimal_point" and "thousands_sep" fields of '
+                   '"localeconv()" if\n'
+                   '     they are non-ASCII or longer than 1 byte, and the '
+                   '"LC_NUMERIC"\n'
+                   '     locale is different than the "LC_CTYPE" locale.  This '
+                   'temporary\n'
+                   '     change affects other threads.\n'
+                   '\n'
+                   '   Changed in version 3.6.5: When formatting a number with '
+                   'the "n"\n'
+                   '   type, the function sets temporarily the "LC_CTYPE" '
+                   'locale to the\n'
+                   '   "LC_NUMERIC" locale in some cases.\n'
+                   '\n'
+                   'str.format_map(mapping)\n'
+                   '\n'
+                   '   Similar to "str.format(**mapping)", except that '
+                   '"mapping" is used\n'
+                   '   directly and not copied to a "dict".  This is useful if '
+                   'for example\n'
+                   '   "mapping" is a dict subclass:\n'
+                   '\n'
+                   '   >>> class Default(dict):\n'
+                   '   ...     def __missing__(self, key):\n'
+                   '   ...         return key\n'
+                   '   ...\n'
+                   "   >>> '{name} was born in "
+                   "{country}'.format_map(Default(name='Guido'))\n"
+                   "   'Guido was born in country'\n"
+                   '\n'
+                   '   New in version 3.2.\n'
+                   '\n'
+                   'str.index(sub[, start[, end]])\n'
+                   '\n'
+                   '   Like "find()", but raise "ValueError" when the '
+                   'substring is not\n'
+                   '   found.\n'
+                   '\n'
+                   'str.isalnum()\n'
+                   '\n'
+                   '   Return true if all characters in the string are '
+                   'alphanumeric and\n'
+                   '   there is at least one character, false otherwise.  A '
+                   'character "c"\n'
+                   '   is alphanumeric if one of the following returns '
+                   '"True":\n'
+                   '   "c.isalpha()", "c.isdecimal()", "c.isdigit()", or '
+                   '"c.isnumeric()".\n'
+                   '\n'
+                   'str.isalpha()\n'
+                   '\n'
+                   '   Return true if all characters in the string are '
+                   'alphabetic and\n'
+                   '   there is at least one character, false otherwise.  '
+                   'Alphabetic\n'
+                   '   characters are those characters defined in the Unicode '
+                   'character\n'
+                   '   database as “Letter”, i.e., those with general category '
+                   'property\n'
+                   '   being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”.  Note '
+                   'that this is\n'
+                   '   different from the “Alphabetic” property defined in the '
+                   'Unicode\n'
+                   '   Standard.\n'
+                   '\n'
+                   'str.isdecimal()\n'
+                   '\n'
+                   '   Return true if all characters in the string are decimal '
+                   'characters\n'
+                   '   and there is at least one character, false otherwise. '
+                   'Decimal\n'
+                   '   characters are those that can be used to form numbers '
+                   'in base 10,\n'
+                   '   e.g. U+0660, ARABIC-INDIC DIGIT ZERO.  Formally a '
+                   'decimal character\n'
+                   '   is a character in the Unicode General Category “Nd”.\n'
+                   '\n'
+                   'str.isdigit()\n'
+                   '\n'
+                   '   Return true if all characters in the string are digits '
+                   'and there is\n'
+                   '   at least one character, false otherwise.  Digits '
+                   'include decimal\n'
+                   '   characters and digits that need special handling, such '
+                   'as the\n'
+                   '   compatibility superscript digits. This covers digits '
+                   'which cannot\n'
+                   '   be used to form numbers in base 10, like the Kharosthi '
+                   'numbers.\n'
+                   '   Formally, a digit is a character that has the property '
+                   'value\n'
+                   '   Numeric_Type=Digit or Numeric_Type=Decimal.\n'
+                   '\n'
+                   'str.isidentifier()\n'
+                   '\n'
+                   '   Return true if the string is a valid identifier '
+                   'according to the\n'
+                   '   language definition, section Identifiers and keywords.\n'
+                   '\n'
+                   '   Use "keyword.iskeyword()" to test for reserved '
+                   'identifiers such as\n'
+                   '   "def" and "class".\n'
+                   '\n'
+                   'str.islower()\n'
+                   '\n'
+                   '   Return true if all cased characters [4] in the string '
+                   'are lowercase\n'
+                   '   and there is at least one cased character, false '
+                   'otherwise.\n'
+                   '\n'
+                   'str.isnumeric()\n'
+                   '\n'
+                   '   Return true if all characters in the string are numeric '
+                   'characters,\n'
+                   '   and there is at least one character, false otherwise. '
+                   'Numeric\n'
+                   '   characters include digit characters, and all characters '
+                   'that have\n'
+                   '   the Unicode numeric value property, e.g. U+2155, VULGAR '
+                   'FRACTION\n'
+                   '   ONE FIFTH.  Formally, numeric characters are those with '
+                   'the\n'
+                   '   property value Numeric_Type=Digit, Numeric_Type=Decimal '
+                   'or\n'
+                   '   Numeric_Type=Numeric.\n'
+                   '\n'
+                   'str.isprintable()\n'
+                   '\n'
+                   '   Return true if all characters in the string are '
+                   'printable or the\n'
+                   '   string is empty, false otherwise.  Nonprintable '
+                   'characters are\n'
+                   '   those characters defined in the Unicode character '
+                   'database as\n'
+                   '   “Other” or “Separator”, excepting the ASCII space '
+                   '(0x20) which is\n'
+                   '   considered printable.  (Note that printable characters '
+                   'in this\n'
+                   '   context are those which should not be escaped when '
+                   '"repr()" is\n'
+                   '   invoked on a string.  It has no bearing on the handling '
+                   'of strings\n'
+                   '   written to "sys.stdout" or "sys.stderr".)\n'
+                   '\n'
+                   'str.isspace()\n'
+                   '\n'
+                   '   Return true if there are only whitespace characters in '
+                   'the string\n'
+                   '   and there is at least one character, false otherwise.  '
+                   'Whitespace\n'
+                   '   characters  are those characters defined in the Unicode '
+                   'character\n'
+                   '   database as “Other” or “Separator” and those with '
+                   'bidirectional\n'
+                   '   property being one of “WS”, “B”, or “S”.\n'
+                   '\n'
+                   'str.istitle()\n'
+                   '\n'
+                   '   Return true if the string is a titlecased string and '
+                   'there is at\n'
+                   '   least one character, for example uppercase characters '
+                   'may only\n'
+                   '   follow uncased characters and lowercase characters only '
+                   'cased ones.\n'
+                   '   Return false otherwise.\n'
+                   '\n'
+                   'str.isupper()\n'
+                   '\n'
+                   '   Return true if all cased characters [4] in the string '
+                   'are uppercase\n'
+                   '   and there is at least one cased character, false '
+                   'otherwise.\n'
+                   '\n'
+                   'str.join(iterable)\n'
+                   '\n'
+                   '   Return a string which is the concatenation of the '
+                   'strings in\n'
+                   '   *iterable*. A "TypeError" will be raised if there are '
+                   'any non-\n'
+                   '   string values in *iterable*, including "bytes" '
+                   'objects.  The\n'
+                   '   separator between elements is the string providing this '
+                   'method.\n'
+                   '\n'
+                   'str.ljust(width[, fillchar])\n'
+                   '\n'
+                   '   Return the string left justified in a string of length '
+                   '*width*.\n'
+                   '   Padding is done using the specified *fillchar* (default '
+                   'is an ASCII\n'
+                   '   space). The original string is returned if *width* is '
+                   'less than or\n'
+                   '   equal to "len(s)".\n'
+                   '\n'
+                   'str.lower()\n'
+                   '\n'
+                   '   Return a copy of the string with all the cased '
+                   'characters [4]\n'
+                   '   converted to lowercase.\n'
+                   '\n'
+                   '   The lowercasing algorithm used is described in section '
+                   '3.13 of the\n'
+                   '   Unicode Standard.\n'
+                   '\n'
+                   'str.lstrip([chars])\n'
+                   '\n'
+                   '   Return a copy of the string with leading characters '
+                   'removed.  The\n'
+                   '   *chars* argument is a string specifying the set of '
+                   'characters to be\n'
+                   '   removed.  If omitted or "None", the *chars* argument '
+                   'defaults to\n'
+                   '   removing whitespace.  The *chars* argument is not a '
+                   'prefix; rather,\n'
+                   '   all combinations of its values are stripped:\n'
+                   '\n'
+                   "      >>> '   spacious   '.lstrip()\n"
+                   "      'spacious   '\n"
+                   "      >>> 'www.example.com'.lstrip('cmowz.')\n"
+                   "      'example.com'\n"
+                   '\n'
+                   'static str.maketrans(x[, y[, z]])\n'
+                   '\n'
+                   '   This static method returns a translation table usable '
+                   'for\n'
+                   '   "str.translate()".\n'
+                   '\n'
+                   '   If there is only one argument, it must be a dictionary '
+                   'mapping\n'
+                   '   Unicode ordinals (integers) or characters (strings of '
+                   'length 1) to\n'
+                   '   Unicode ordinals, strings (of arbitrary lengths) or '
+                   '"None".\n'
+                   '   Character keys will then be converted to ordinals.\n'
+                   '\n'
+                   '   If there are two arguments, they must be strings of '
+                   'equal length,\n'
+                   '   and in the resulting dictionary, each character in x '
+                   'will be mapped\n'
+                   '   to the character at the same position in y.  If there '
+                   'is a third\n'
+                   '   argument, it must be a string, whose characters will be '
+                   'mapped to\n'
+                   '   "None" in the result.\n'
+                   '\n'
+                   'str.partition(sep)\n'
+                   '\n'
+                   '   Split the string at the first occurrence of *sep*, and '
+                   'return a\n'
+                   '   3-tuple containing the part before the separator, the '
+                   'separator\n'
+                   '   itself, and the part after the separator.  If the '
+                   'separator is not\n'
+                   '   found, return a 3-tuple containing the string itself, '
+                   'followed by\n'
+                   '   two empty strings.\n'
+                   '\n'
+                   'str.replace(old, new[, count])\n'
+                   '\n'
+                   '   Return a copy of the string with all occurrences of '
+                   'substring *old*\n'
+                   '   replaced by *new*.  If the optional argument *count* is '
+                   'given, only\n'
+                   '   the first *count* occurrences are replaced.\n'
+                   '\n'
+                   'str.rfind(sub[, start[, end]])\n'
+                   '\n'
+                   '   Return the highest index in the string where substring '
+                   '*sub* is\n'
+                   '   found, such that *sub* is contained within '
+                   '"s[start:end]".\n'
+                   '   Optional arguments *start* and *end* are interpreted as '
+                   'in slice\n'
+                   '   notation.  Return "-1" on failure.\n'
+                   '\n'
+                   'str.rindex(sub[, start[, end]])\n'
+                   '\n'
+                   '   Like "rfind()" but raises "ValueError" when the '
+                   'substring *sub* is\n'
+                   '   not found.\n'
+                   '\n'
+                   'str.rjust(width[, fillchar])\n'
+                   '\n'
+                   '   Return the string right justified in a string of length '
+                   '*width*.\n'
+                   '   Padding is done using the specified *fillchar* (default '
+                   'is an ASCII\n'
+                   '   space). The original string is returned if *width* is '
+                   'less than or\n'
+                   '   equal to "len(s)".\n'
+                   '\n'
+                   'str.rpartition(sep)\n'
+                   '\n'
+                   '   Split the string at the last occurrence of *sep*, and '
+                   'return a\n'
+                   '   3-tuple containing the part before the separator, the '
+                   'separator\n'
+                   '   itself, and the part after the separator.  If the '
+                   'separator is not\n'
+                   '   found, return a 3-tuple containing two empty strings, '
+                   'followed by\n'
+                   '   the string itself.\n'
+                   '\n'
+                   'str.rsplit(sep=None, maxsplit=-1)\n'
+                   '\n'
+                   '   Return a list of the words in the string, using *sep* '
+                   'as the\n'
+                   '   delimiter string. If *maxsplit* is given, at most '
+                   '*maxsplit* splits\n'
+                   '   are done, the *rightmost* ones.  If *sep* is not '
+                   'specified or\n'
+                   '   "None", any whitespace string is a separator.  Except '
+                   'for splitting\n'
+                   '   from the right, "rsplit()" behaves like "split()" which '
+                   'is\n'
+                   '   described in detail below.\n'
+                   '\n'
+                   'str.rstrip([chars])\n'
+                   '\n'
+                   '   Return a copy of the string with trailing characters '
+                   'removed.  The\n'
+                   '   *chars* argument is a string specifying the set of '
+                   'characters to be\n'
+                   '   removed.  If omitted or "None", the *chars* argument '
+                   'defaults to\n'
+                   '   removing whitespace.  The *chars* argument is not a '
+                   'suffix; rather,\n'
+                   '   all combinations of its values are stripped:\n'
+                   '\n'
+                   "      >>> '   spacious   '.rstrip()\n"
+                   "      '   spacious'\n"
+                   "      >>> 'mississippi'.rstrip('ipz')\n"
+                   "      'mississ'\n"
+                   '\n'
+                   'str.split(sep=None, maxsplit=-1)\n'
+                   '\n'
+                   '   Return a list of the words in the string, using *sep* '
+                   'as the\n'
+                   '   delimiter string.  If *maxsplit* is given, at most '
+                   '*maxsplit*\n'
+                   '   splits are done (thus, the list will have at most '
+                   '"maxsplit+1"\n'
+                   '   elements).  If *maxsplit* is not specified or "-1", '
+                   'then there is\n'
+                   '   no limit on the number of splits (all possible splits '
+                   'are made).\n'
+                   '\n'
+                   '   If *sep* is given, consecutive delimiters are not '
+                   'grouped together\n'
+                   '   and are deemed to delimit empty strings (for example,\n'
+                   '   "\'1,,2\'.split(\',\')" returns "[\'1\', \'\', '
+                   '\'2\']").  The *sep* argument\n'
+                   '   may consist of multiple characters (for example,\n'
+                   '   "\'1<>2<>3\'.split(\'<>\')" returns "[\'1\', \'2\', '
+                   '\'3\']"). Splitting an\n'
+                   '   empty string with a specified separator returns '
+                   '"[\'\']".\n'
+                   '\n'
+                   '   For example:\n'
+                   '\n'
+                   "      >>> '1,2,3'.split(',')\n"
+                   "      ['1', '2', '3']\n"
+                   "      >>> '1,2,3'.split(',', maxsplit=1)\n"
+                   "      ['1', '2,3']\n"
+                   "      >>> '1,2,,3,'.split(',')\n"
+                   "      ['1', '2', '', '3', '']\n"
+                   '\n'
+                   '   If *sep* is not specified or is "None", a different '
+                   'splitting\n'
+                   '   algorithm is applied: runs of consecutive whitespace '
+                   'are regarded\n'
+                   '   as a single separator, and the result will contain no '
+                   'empty strings\n'
+                   '   at the start or end if the string has leading or '
+                   'trailing\n'
+                   '   whitespace.  Consequently, splitting an empty string or '
+                   'a string\n'
+                   '   consisting of just whitespace with a "None" separator '
+                   'returns "[]".\n'
+                   '\n'
+                   '   For example:\n'
+                   '\n'
+                   "      >>> '1 2 3'.split()\n"
+                   "      ['1', '2', '3']\n"
+                   "      >>> '1 2 3'.split(maxsplit=1)\n"
+                   "      ['1', '2 3']\n"
+                   "      >>> '   1   2   3   '.split()\n"
+                   "      ['1', '2', '3']\n"
+                   '\n'
+                   'str.splitlines([keepends])\n'
+                   '\n'
+                   '   Return a list of the lines in the string, breaking at '
+                   'line\n'
+                   '   boundaries.  Line breaks are not included in the '
+                   'resulting list\n'
+                   '   unless *keepends* is given and true.\n'
+                   '\n'
+                   '   This method splits on the following line boundaries.  '
+                   'In\n'
+                   '   particular, the boundaries are a superset of *universal '
+                   'newlines*.\n'
+                   '\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | Representation          | '
+                   'Description                   |\n'
+                   '   '
+                   '+=========================+===============================+\n'
+                   '   | "\\n"                    | Line '
+                   'Feed                     |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\r"                    | Carriage '
+                   'Return               |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\r\\n"                  | Carriage Return + Line '
+                   'Feed   |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\v" or "\\x0b"          | Line '
+                   'Tabulation               |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\f" or "\\x0c"          | Form '
+                   'Feed                     |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\x1c"                  | File '
+                   'Separator                |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\x1d"                  | Group '
+                   'Separator               |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\x1e"                  | Record '
+                   'Separator              |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\x85"                  | Next Line (C1 Control '
+                   'Code)   |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\u2028"                | Line '
+                   'Separator                |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '   | "\\u2029"                | Paragraph '
+                   'Separator           |\n'
+                   '   '
+                   '+-------------------------+-------------------------------+\n'
+                   '\n'
+                   '   Changed in version 3.2: "\\v" and "\\f" added to list '
+                   'of line\n'
+                   '   boundaries.\n'
+                   '\n'
+                   '   For example:\n'
+                   '\n'
+                   "      >>> 'ab c\\n\\nde fg\\rkl\\r\\n'.splitlines()\n"
+                   "      ['ab c', '', 'de fg', 'kl']\n"
+                   "      >>> 'ab c\\n\\nde "
+                   "fg\\rkl\\r\\n'.splitlines(keepends=True)\n"
+                   "      ['ab c\\n', '\\n', 'de fg\\r', 'kl\\r\\n']\n"
+                   '\n'
+                   '   Unlike "split()" when a delimiter string *sep* is '
+                   'given, this\n'
+                   '   method returns an empty list for the empty string, and '
+                   'a terminal\n'
+                   '   line break does not result in an extra line:\n'
+                   '\n'
+                   '      >>> "".splitlines()\n'
+                   '      []\n'
+                   '      >>> "One line\\n".splitlines()\n'
+                   "      ['One line']\n"
+                   '\n'
+                   '   For comparison, "split(\'\\n\')" gives:\n'
+                   '\n'
+                   "      >>> ''.split('\\n')\n"
+                   "      ['']\n"
+                   "      >>> 'Two lines\\n'.split('\\n')\n"
+                   "      ['Two lines', '']\n"
+                   '\n'
+                   'str.startswith(prefix[, start[, end]])\n'
+                   '\n'
+                   '   Return "True" if string starts with the *prefix*, '
+                   'otherwise return\n'
+                   '   "False". *prefix* can also be a tuple of prefixes to '
+                   'look for.\n'
+                   '   With optional *start*, test string beginning at that '
+                   'position.\n'
+                   '   With optional *end*, stop comparing string at that '
+                   'position.\n'
+                   '\n'
+                   'str.strip([chars])\n'
+                   '\n'
+                   '   Return a copy of the string with the leading and '
+                   'trailing\n'
+                   '   characters removed. The *chars* argument is a string '
+                   'specifying the\n'
+                   '   set of characters to be removed. If omitted or "None", '
+                   'the *chars*\n'
+                   '   argument defaults to removing whitespace. The *chars* '
+                   'argument is\n'
+                   '   not a prefix or suffix; rather, all combinations of its '
+                   'values are\n'
+                   '   stripped:\n'
+                   '\n'
+                   "      >>> '   spacious   '.strip()\n"
+                   "      'spacious'\n"
+                   "      >>> 'www.example.com'.strip('cmowz.')\n"
+                   "      'example'\n"
+                   '\n'
+                   '   The outermost leading and trailing *chars* argument '
+                   'values are\n'
+                   '   stripped from the string. Characters are removed from '
+                   'the leading\n'
+                   '   end until reaching a string character that is not '
+                   'contained in the\n'
+                   '   set of characters in *chars*. A similar action takes '
+                   'place on the\n'
+                   '   trailing end. For example:\n'
+                   '\n'
+                   "      >>> comment_string = '#....... Section 3.2.1 Issue "
+                   "#32 .......'\n"
+                   "      >>> comment_string.strip('.#! ')\n"
+                   "      'Section 3.2.1 Issue #32'\n"
+                   '\n'
+                   'str.swapcase()\n'
+                   '\n'
+                   '   Return a copy of the string with uppercase characters '
+                   'converted to\n'
+                   '   lowercase and vice versa. Note that it is not '
+                   'necessarily true that\n'
+                   '   "s.swapcase().swapcase() == s".\n'
+                   '\n'
+                   'str.title()\n'
+                   '\n'
+                   '   Return a titlecased version of the string where words '
+                   'start with an\n'
+                   '   uppercase character and the remaining characters are '
+                   'lowercase.\n'
+                   '\n'
+                   '   For example:\n'
+                   '\n'
+                   "      >>> 'Hello world'.title()\n"
+                   "      'Hello World'\n"
+                   '\n'
+                   '   The algorithm uses a simple language-independent '
+                   'definition of a\n'
+                   '   word as groups of consecutive letters.  The definition '
+                   'works in\n'
+                   '   many contexts but it means that apostrophes in '
+                   'contractions and\n'
+                   '   possessives form word boundaries, which may not be the '
+                   'desired\n'
+                   '   result:\n'
+                   '\n'
+                   '      >>> "they\'re bill\'s friends from the UK".title()\n'
+                   '      "They\'Re Bill\'S Friends From The Uk"\n'
+                   '\n'
+                   '   A workaround for apostrophes can be constructed using '
+                   'regular\n'
+                   '   expressions:\n'
+                   '\n'
+                   '      >>> import re\n'
+                   '      >>> def titlecase(s):\n'
+                   '      ...     return re.sub(r"[A-Za-z]+(\'[A-Za-z]+)?",\n'
+                   '      ...                   lambda mo: '
+                   'mo.group(0)[0].upper() +\n'
+                   '      ...                              '
+                   'mo.group(0)[1:].lower(),\n'
+                   '      ...                   s)\n'
+                   '      ...\n'
+                   '      >>> titlecase("they\'re bill\'s friends.")\n'
+                   '      "They\'re Bill\'s Friends."\n'
+                   '\n'
+                   'str.translate(table)\n'
+                   '\n'
+                   '   Return a copy of the string in which each character has '
+                   'been mapped\n'
+                   '   through the given translation table.  The table must be '
+                   'an object\n'
+                   '   that implements indexing via "__getitem__()", typically '
+                   'a *mapping*\n'
+                   '   or *sequence*.  When indexed by a Unicode ordinal (an '
+                   'integer), the\n'
+                   '   table object can do any of the following: return a '
+                   'Unicode ordinal\n'
+                   '   or a string, to map the character to one or more other '
+                   'characters;\n'
+                   '   return "None", to delete the character from the return '
+                   'string; or\n'
+                   '   raise a "LookupError" exception, to map the character '
+                   'to itself.\n'
+                   '\n'
+                   '   You can use "str.maketrans()" to create a translation '
+                   'map from\n'
+                   '   character-to-character mappings in different formats.\n'
+                   '\n'
+                   '   See also the "codecs" module for a more flexible '
+                   'approach to custom\n'
+                   '   character mappings.\n'
+                   '\n'
+                   'str.upper()\n'
+                   '\n'
+                   '   Return a copy of the string with all the cased '
+                   'characters [4]\n'
+                   '   converted to uppercase.  Note that '
+                   '"s.upper().isupper()" might be\n'
+                   '   "False" if "s" contains uncased characters or if the '
+                   'Unicode\n'
+                   '   category of the resulting character(s) is not “Lu” '
+                   '(Letter,\n'
+                   '   uppercase), but e.g. “Lt” (Letter, titlecase).\n'
+                   '\n'
+                   '   The uppercasing algorithm used is described in section '
+                   '3.13 of the\n'
+                   '   Unicode Standard.\n'
+                   '\n'
+                   'str.zfill(width)\n'
+                   '\n'
+                   '   Return a copy of the string left filled with ASCII '
+                   '"\'0\'" digits to\n'
+                   '   make a string of length *width*. A leading sign prefix\n'
+                   '   ("\'+\'"/"\'-\'") is handled by inserting the padding '
+                   '*after* the sign\n'
+                   '   character rather than before. The original string is '
+                   'returned if\n'
+                   '   *width* is less than or equal to "len(s)".\n'
+                   '\n'
+                   '   For example:\n'
+                   '\n'
+                   '      >>> "42".zfill(5)\n'
+                   "      '00042'\n"
+                   '      >>> "-42".zfill(5)\n'
+                   "      '-0042'\n",
+ 'strings': 'String and Bytes literals\n'
+            '*************************\n'
+            '\n'
+            'String literals are described by the following lexical '
+            'definitions:\n'
+            '\n'
+            '   stringliteral   ::= [stringprefix](shortstring | longstring)\n'
+            '   stringprefix    ::= "r" | "u" | "R" | "U" | "f" | "F"\n'
+            '                    | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | '
+            '"Rf" | "RF"\n'
+            '   shortstring     ::= "\'" shortstringitem* "\'" | \'"\' '
+            'shortstringitem* \'"\'\n'
+            '   longstring      ::= "\'\'\'" longstringitem* "\'\'\'" | '
+            '\'"""\' longstringitem* \'"""\'\n'
+            '   shortstringitem ::= shortstringchar | stringescapeseq\n'
+            '   longstringitem  ::= longstringchar | stringescapeseq\n'
+            '   shortstringchar ::= <any source character except "\\" or '
+            'newline or the quote>\n'
+            '   longstringchar  ::= <any source character except "\\">\n'
+            '   stringescapeseq ::= "\\" <any source character>\n'
+            '\n'
+            '   bytesliteral   ::= bytesprefix(shortbytes | longbytes)\n'
+            '   bytesprefix    ::= "b" | "B" | "br" | "Br" | "bR" | "BR" | '
+            '"rb" | "rB" | "Rb" | "RB"\n'
+            '   shortbytes     ::= "\'" shortbytesitem* "\'" | \'"\' '
+            'shortbytesitem* \'"\'\n'
+            '   longbytes      ::= "\'\'\'" longbytesitem* "\'\'\'" | \'"""\' '
+            'longbytesitem* \'"""\'\n'
+            '   shortbytesitem ::= shortbyteschar | bytesescapeseq\n'
+            '   longbytesitem  ::= longbyteschar | bytesescapeseq\n'
+            '   shortbyteschar ::= <any ASCII character except "\\" or newline '
+            'or the quote>\n'
+            '   longbyteschar  ::= <any ASCII character except "\\">\n'
+            '   bytesescapeseq ::= "\\" <any ASCII character>\n'
+            '\n'
+            'One syntactic restriction not indicated by these productions is '
+            'that\n'
+            'whitespace is not allowed between the "stringprefix" or '
+            '"bytesprefix"\n'
+            'and the rest of the literal. The source character set is defined '
+            'by\n'
+            'the encoding declaration; it is UTF-8 if no encoding declaration '
+            'is\n'
+            'given in the source file; see section Encoding declarations.\n'
+            '\n'
+            'In plain English: Both types of literals can be enclosed in '
+            'matching\n'
+            'single quotes ("\'") or double quotes (""").  They can also be '
+            'enclosed\n'
+            'in matching groups of three single or double quotes (these are\n'
+            'generally referred to as *triple-quoted strings*).  The '
+            'backslash\n'
+            '("\\") character is used to escape characters that otherwise have '
+            'a\n'
+            'special meaning, such as newline, backslash itself, or the quote\n'
+            'character.\n'
+            '\n'
+            'Bytes literals are always prefixed with "\'b\'" or "\'B\'"; they '
+            'produce\n'
+            'an instance of the "bytes" type instead of the "str" type.  They '
+            'may\n'
+            'only contain ASCII characters; bytes with a numeric value of 128 '
+            'or\n'
+            'greater must be expressed with escapes.\n'
+            '\n'
+            'Both string and bytes literals may optionally be prefixed with a\n'
+            'letter "\'r\'" or "\'R\'"; such strings are called *raw strings* '
+            'and treat\n'
+            'backslashes as literal characters.  As a result, in string '
+            'literals,\n'
+            '"\'\\U\'" and "\'\\u\'" escapes in raw strings are not treated '
+            'specially.\n'
+            'Given that Python 2.x’s raw unicode literals behave differently '
+            'than\n'
+            'Python 3.x’s the "\'ur\'" syntax is not supported.\n'
+            '\n'
+            'New in version 3.3: The "\'rb\'" prefix of raw bytes literals has '
+            'been\n'
+            'added as a synonym of "\'br\'".\n'
+            '\n'
+            'New in version 3.3: Support for the unicode legacy literal\n'
+            '("u\'value\'") was reintroduced to simplify the maintenance of '
+            'dual\n'
+            'Python 2.x and 3.x codebases. See **PEP 414** for more '
+            'information.\n'
+            '\n'
+            'A string literal with "\'f\'" or "\'F\'" in its prefix is a '
+            '*formatted\n'
+            'string literal*; see Formatted string literals.  The "\'f\'" may '
+            'be\n'
+            'combined with "\'r\'", but not with "\'b\'" or "\'u\'", therefore '
+            'raw\n'
+            'formatted strings are possible, but formatted bytes literals are '
+            'not.\n'
+            '\n'
+            'In triple-quoted literals, unescaped newlines and quotes are '
+            'allowed\n'
+            '(and are retained), except that three unescaped quotes in a row\n'
+            'terminate the literal.  (A “quote” is the character used to open '
+            'the\n'
+            'literal, i.e. either "\'" or """.)\n'
+            '\n'
+            'Unless an "\'r\'" or "\'R\'" prefix is present, escape sequences '
+            'in string\n'
+            'and bytes literals are interpreted according to rules similar to '
+            'those\n'
+            'used by Standard C.  The recognized escape sequences are:\n'
+            '\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| Escape Sequence   | Meaning                           | Notes   '
+            '|\n'
+            '+===================+===================================+=========+\n'
+            '| "\\newline"        | Backslash and newline ignored     '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\\\"              | Backslash ("\\")                   '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\\'"              | Single quote ("\'")                '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\""              | Double quote (""")                '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\a"              | ASCII Bell (BEL)                  '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\b"              | ASCII Backspace (BS)              '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\f"              | ASCII Formfeed (FF)               '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\n"              | ASCII Linefeed (LF)               '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\r"              | ASCII Carriage Return (CR)        '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\t"              | ASCII Horizontal Tab (TAB)        '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\v"              | ASCII Vertical Tab (VT)           '
+            '|         |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\ooo"            | Character with octal value *ooo*  | '
+            '(1,3)   |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\xhh"            | Character with hex value *hh*     | '
+            '(2,3)   |\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '\n'
+            'Escape sequences only recognized in string literals are:\n'
+            '\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| Escape Sequence   | Meaning                           | Notes   '
+            '|\n'
+            '+===================+===================================+=========+\n'
+            '| "\\N{name}"        | Character named *name* in the     | '
+            '(4)     |\n'
+            '|                   | Unicode database                  |         '
+            '|\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\uxxxx"          | Character with 16-bit hex value   | '
+            '(5)     |\n'
+            '|                   | *xxxx*                            |         '
+            '|\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '| "\\Uxxxxxxxx"      | Character with 32-bit hex value   | '
+            '(6)     |\n'
+            '|                   | *xxxxxxxx*                        |         '
+            '|\n'
+            '+-------------------+-----------------------------------+---------+\n'
+            '\n'
+            'Notes:\n'
+            '\n'
+            '1. As in Standard C, up to three octal digits are accepted.\n'
+            '\n'
+            '2. Unlike in Standard C, exactly two hex digits are required.\n'
+            '\n'
+            '3. In a bytes literal, hexadecimal and octal escapes denote the\n'
+            '   byte with the given value. In a string literal, these escapes\n'
+            '   denote a Unicode character with the given value.\n'
+            '\n'
+            '4. Changed in version 3.3: Support for name aliases [1] has been\n'
+            '   added.\n'
+            '\n'
+            '5. Exactly four hex digits are required.\n'
+            '\n'
+            '6. Any Unicode character can be encoded this way.  Exactly eight\n'
+            '   hex digits are required.\n'
+            '\n'
+            'Unlike Standard C, all unrecognized escape sequences are left in '
+            'the\n'
+            'string unchanged, i.e., *the backslash is left in the result*.  '
+            '(This\n'
+            'behavior is useful when debugging: if an escape sequence is '
+            'mistyped,\n'
+            'the resulting output is more easily recognized as broken.)  It is '
+            'also\n'
+            'important to note that the escape sequences only recognized in '
+            'string\n'
+            'literals fall into the category of unrecognized escapes for '
+            'bytes\n'
+            'literals.\n'
+            '\n'
+            '   Changed in version 3.6: Unrecognized escape sequences produce '
+            'a\n'
+            '   DeprecationWarning.  In some future version of Python they '
+            'will be\n'
+            '   a SyntaxError.\n'
+            '\n'
+            'Even in a raw literal, quotes can be escaped with a backslash, '
+            'but the\n'
+            'backslash remains in the result; for example, "r"\\""" is a '
+            'valid\n'
+            'string literal consisting of two characters: a backslash and a '
+            'double\n'
+            'quote; "r"\\"" is not a valid string literal (even a raw string '
+            'cannot\n'
+            'end in an odd number of backslashes).  Specifically, *a raw '
+            'literal\n'
+            'cannot end in a single backslash* (since the backslash would '
+            'escape\n'
+            'the following quote character).  Note also that a single '
+            'backslash\n'
+            'followed by a newline is interpreted as those two characters as '
+            'part\n'
+            'of the literal, *not* as a line continuation.\n',
+ 'subscriptions': 'Subscriptions\n'
+                  '*************\n'
+                  '\n'
+                  'A subscription selects an item of a sequence (string, tuple '
+                  'or list)\n'
+                  'or mapping (dictionary) object:\n'
+                  '\n'
+                  '   subscription ::= primary "[" expression_list "]"\n'
+                  '\n'
+                  'The primary must evaluate to an object that supports '
+                  'subscription\n'
+                  '(lists or dictionaries for example).  User-defined objects '
+                  'can support\n'
+                  'subscription by defining a "__getitem__()" method.\n'
+                  '\n'
+                  'For built-in objects, there are two types of objects that '
+                  'support\n'
+                  'subscription:\n'
+                  '\n'
+                  'If the primary is a mapping, the expression list must '
+                  'evaluate to an\n'
+                  'object whose value is one of the keys of the mapping, and '
+                  'the\n'
+                  'subscription selects the value in the mapping that '
+                  'corresponds to that\n'
+                  'key.  (The expression list is a tuple except if it has '
+                  'exactly one\n'
+                  'item.)\n'
+                  '\n'
+                  'If the primary is a sequence, the expression list must '
+                  'evaluate to an\n'
+                  'integer or a slice (as discussed in the following '
+                  'section).\n'
+                  '\n'
+                  'The formal syntax makes no special provision for negative '
+                  'indices in\n'
+                  'sequences; however, built-in sequences all provide a '
+                  '"__getitem__()"\n'
+                  'method that interprets negative indices by adding the '
+                  'length of the\n'
+                  'sequence to the index (so that "x[-1]" selects the last '
+                  'item of "x").\n'
+                  'The resulting value must be a nonnegative integer less than '
+                  'the number\n'
+                  'of items in the sequence, and the subscription selects the '
+                  'item whose\n'
+                  'index is that value (counting from zero). Since the support '
+                  'for\n'
+                  'negative indices and slicing occurs in the object’s '
+                  '"__getitem__()"\n'
+                  'method, subclasses overriding this method will need to '
+                  'explicitly add\n'
+                  'that support.\n'
+                  '\n'
+                  'A string’s items are characters.  A character is not a '
+                  'separate data\n'
+                  'type but a string of exactly one character.\n',
+ 'truth': 'Truth Value Testing\n'
+          '*******************\n'
+          '\n'
+          'Any object can be tested for truth value, for use in an "if" or\n'
+          '"while" condition or as operand of the Boolean operations below.\n'
+          '\n'
+          'By default, an object is considered true unless its class defines\n'
+          'either a "__bool__()" method that returns "False" or a "__len__()"\n'
+          'method that returns zero, when called with the object. [1]  Here '
+          'are\n'
+          'most of the built-in objects considered false:\n'
+          '\n'
+          '* constants defined to be false: "None" and "False".\n'
+          '\n'
+          '* zero of any numeric type: "0", "0.0", "0j", "Decimal(0)",\n'
+          '  "Fraction(0, 1)"\n'
+          '\n'
+          '* empty sequences and collections: "\'\'", "()", "[]", "{}", '
+          '"set()",\n'
+          '  "range(0)"\n'
+          '\n'
+          'Operations and built-in functions that have a Boolean result '
+          'always\n'
+          'return "0" or "False" for false and "1" or "True" for true, unless\n'
+          'otherwise stated. (Important exception: the Boolean operations '
+          '"or"\n'
+          'and "and" always return one of their operands.)\n',
+ 'try': 'The "try" statement\n'
+        '*******************\n'
+        '\n'
+        'The "try" statement specifies exception handlers and/or cleanup code\n'
+        'for a group of statements:\n'
+        '\n'
+        '   try_stmt  ::= try1_stmt | try2_stmt\n'
+        '   try1_stmt ::= "try" ":" suite\n'
+        '                 ("except" [expression ["as" identifier]] ":" '
+        'suite)+\n'
+        '                 ["else" ":" suite]\n'
+        '                 ["finally" ":" suite]\n'
+        '   try2_stmt ::= "try" ":" suite\n'
+        '                 "finally" ":" suite\n'
+        '\n'
+        'The "except" clause(s) specify one or more exception handlers. When '
+        'no\n'
+        'exception occurs in the "try" clause, no exception handler is\n'
+        'executed. When an exception occurs in the "try" suite, a search for '
+        'an\n'
+        'exception handler is started.  This search inspects the except '
+        'clauses\n'
+        'in turn until one is found that matches the exception.  An '
+        'expression-\n'
+        'less except clause, if present, must be last; it matches any\n'
+        'exception.  For an except clause with an expression, that expression\n'
+        'is evaluated, and the clause matches the exception if the resulting\n'
+        'object is “compatible” with the exception.  An object is compatible\n'
+        'with an exception if it is the class or a base class of the '
+        'exception\n'
+        'object or a tuple containing an item compatible with the exception.\n'
+        '\n'
+        'If no except clause matches the exception, the search for an '
+        'exception\n'
+        'handler continues in the surrounding code and on the invocation '
+        'stack.\n'
+        '[1]\n'
+        '\n'
+        'If the evaluation of an expression in the header of an except clause\n'
+        'raises an exception, the original search for a handler is canceled '
+        'and\n'
+        'a search starts for the new exception in the surrounding code and on\n'
+        'the call stack (it is treated as if the entire "try" statement '
+        'raised\n'
+        'the exception).\n'
+        '\n'
+        'When a matching except clause is found, the exception is assigned to\n'
+        'the target specified after the "as" keyword in that except clause, '
+        'if\n'
+        'present, and the except clause’s suite is executed.  All except\n'
+        'clauses must have an executable block.  When the end of this block '
+        'is\n'
+        'reached, execution continues normally after the entire try '
+        'statement.\n'
+        '(This means that if two nested handlers exist for the same '
+        'exception,\n'
+        'and the exception occurs in the try clause of the inner handler, the\n'
+        'outer handler will not handle the exception.)\n'
+        '\n'
+        'When an exception has been assigned using "as target", it is cleared\n'
+        'at the end of the except clause.  This is as if\n'
+        '\n'
+        '   except E as N:\n'
+        '       foo\n'
+        '\n'
+        'was translated to\n'
+        '\n'
+        '   except E as N:\n'
+        '       try:\n'
+        '           foo\n'
+        '       finally:\n'
+        '           del N\n'
+        '\n'
+        'This means the exception must be assigned to a different name to be\n'
+        'able to refer to it after the except clause.  Exceptions are cleared\n'
+        'because with the traceback attached to them, they form a reference\n'
+        'cycle with the stack frame, keeping all locals in that frame alive\n'
+        'until the next garbage collection occurs.\n'
+        '\n'
+        'Before an except clause’s suite is executed, details about the\n'
+        'exception are stored in the "sys" module and can be accessed via\n'
+        '"sys.exc_info()". "sys.exc_info()" returns a 3-tuple consisting of '
+        'the\n'
+        'exception class, the exception instance and a traceback object (see\n'
+        'section The standard type hierarchy) identifying the point in the\n'
+        'program where the exception occurred.  "sys.exc_info()" values are\n'
+        'restored to their previous values (before the call) when returning\n'
+        'from a function that handled an exception.\n'
+        '\n'
+        'The optional "else" clause is executed if the control flow leaves '
+        'the\n'
+        '"try" suite, no exception was raised, and no "return", "continue", '
+        'or\n'
+        '"break" statement was executed.  Exceptions in the "else" clause are\n'
+        'not handled by the preceding "except" clauses.\n'
+        '\n'
+        'If "finally" is present, it specifies a ‘cleanup’ handler.  The '
+        '"try"\n'
+        'clause is executed, including any "except" and "else" clauses.  If '
+        'an\n'
+        'exception occurs in any of the clauses and is not handled, the\n'
+        'exception is temporarily saved. The "finally" clause is executed.  '
+        'If\n'
+        'there is a saved exception it is re-raised at the end of the '
+        '"finally"\n'
+        'clause.  If the "finally" clause raises another exception, the saved\n'
+        'exception is set as the context of the new exception. If the '
+        '"finally"\n'
+        'clause executes a "return" or "break" statement, the saved exception\n'
+        'is discarded:\n'
+        '\n'
+        '   >>> def f():\n'
+        '   ...     try:\n'
+        '   ...         1/0\n'
+        '   ...     finally:\n'
+        '   ...         return 42\n'
+        '   ...\n'
+        '   >>> f()\n'
+        '   42\n'
+        '\n'
+        'The exception information is not available to the program during\n'
+        'execution of the "finally" clause.\n'
+        '\n'
+        'When a "return", "break" or "continue" statement is executed in the\n'
+        '"try" suite of a "try"…"finally" statement, the "finally" clause is\n'
+        'also executed ‘on the way out.’ A "continue" statement is illegal in\n'
+        'the "finally" clause. (The reason is a problem with the current\n'
+        'implementation — this restriction may be lifted in the future).\n'
+        '\n'
+        'The return value of a function is determined by the last "return"\n'
+        'statement executed.  Since the "finally" clause always executes, a\n'
+        '"return" statement executed in the "finally" clause will always be '
+        'the\n'
+        'last one executed:\n'
+        '\n'
+        '   >>> def foo():\n'
+        '   ...     try:\n'
+        "   ...         return 'try'\n"
+        '   ...     finally:\n'
+        "   ...         return 'finally'\n"
+        '   ...\n'
+        '   >>> foo()\n'
+        "   'finally'\n"
+        '\n'
+        'Additional information on exceptions can be found in section\n'
+        'Exceptions, and information on using the "raise" statement to '
+        'generate\n'
+        'exceptions may be found in section The raise statement.\n',
+ 'types': 'The standard type hierarchy\n'
+          '***************************\n'
+          '\n'
+          'Below is a list of the types that are built into Python.  '
+          'Extension\n'
+          'modules (written in C, Java, or other languages, depending on the\n'
+          'implementation) can define additional types.  Future versions of\n'
+          'Python may add types to the type hierarchy (e.g., rational '
+          'numbers,\n'
+          'efficiently stored arrays of integers, etc.), although such '
+          'additions\n'
+          'will often be provided via the standard library instead.\n'
+          '\n'
+          'Some of the type descriptions below contain a paragraph listing\n'
+          '‘special attributes.’  These are attributes that provide access to '
+          'the\n'
+          'implementation and are not intended for general use.  Their '
+          'definition\n'
+          'may change in the future.\n'
+          '\n'
+          'None\n'
+          '   This type has a single value.  There is a single object with '
+          'this\n'
+          '   value. This object is accessed through the built-in name "None". '
+          'It\n'
+          '   is used to signify the absence of a value in many situations, '
+          'e.g.,\n'
+          '   it is returned from functions that don’t explicitly return\n'
+          '   anything. Its truth value is false.\n'
+          '\n'
+          'NotImplemented\n'
+          '   This type has a single value.  There is a single object with '
+          'this\n'
+          '   value. This object is accessed through the built-in name\n'
+          '   "NotImplemented". Numeric methods and rich comparison methods\n'
+          '   should return this value if they do not implement the operation '
+          'for\n'
+          '   the operands provided.  (The interpreter will then try the\n'
+          '   reflected operation, or some other fallback, depending on the\n'
+          '   operator.)  Its truth value is true.\n'
+          '\n'
+          '   See Implementing the arithmetic operations for more details.\n'
+          '\n'
+          'Ellipsis\n'
+          '   This type has a single value.  There is a single object with '
+          'this\n'
+          '   value. This object is accessed through the literal "..." or the\n'
+          '   built-in name "Ellipsis".  Its truth value is true.\n'
+          '\n'
+          '"numbers.Number"\n'
+          '   These are created by numeric literals and returned as results '
+          'by\n'
+          '   arithmetic operators and arithmetic built-in functions.  '
+          'Numeric\n'
+          '   objects are immutable; once created their value never changes.\n'
+          '   Python numbers are of course strongly related to mathematical\n'
+          '   numbers, but subject to the limitations of numerical '
+          'representation\n'
+          '   in computers.\n'
+          '\n'
+          '   Python distinguishes between integers, floating point numbers, '
+          'and\n'
+          '   complex numbers:\n'
+          '\n'
+          '   "numbers.Integral"\n'
+          '      These represent elements from the mathematical set of '
+          'integers\n'
+          '      (positive and negative).\n'
+          '\n'
+          '      There are two types of integers:\n'
+          '\n'
+          '      Integers ("int")\n'
+          '\n'
+          '         These represent numbers in an unlimited range, subject to\n'
+          '         available (virtual) memory only.  For the purpose of '
+          'shift\n'
+          '         and mask operations, a binary representation is assumed, '
+          'and\n'
+          '         negative numbers are represented in a variant of 2’s\n'
+          '         complement which gives the illusion of an infinite string '
+          'of\n'
+          '         sign bits extending to the left.\n'
+          '\n'
+          '      Booleans ("bool")\n'
+          '         These represent the truth values False and True.  The two\n'
+          '         objects representing the values "False" and "True" are '
+          'the\n'
+          '         only Boolean objects. The Boolean type is a subtype of '
+          'the\n'
+          '         integer type, and Boolean values behave like the values 0 '
+          'and\n'
+          '         1, respectively, in almost all contexts, the exception '
+          'being\n'
+          '         that when converted to a string, the strings ""False"" or\n'
+          '         ""True"" are returned, respectively.\n'
+          '\n'
+          '      The rules for integer representation are intended to give '
+          'the\n'
+          '      most meaningful interpretation of shift and mask operations\n'
+          '      involving negative integers.\n'
+          '\n'
+          '   "numbers.Real" ("float")\n'
+          '      These represent machine-level double precision floating '
+          'point\n'
+          '      numbers. You are at the mercy of the underlying machine\n'
+          '      architecture (and C or Java implementation) for the accepted\n'
+          '      range and handling of overflow. Python does not support '
+          'single-\n'
+          '      precision floating point numbers; the savings in processor '
+          'and\n'
+          '      memory usage that are usually the reason for using these are\n'
+          '      dwarfed by the overhead of using objects in Python, so there '
+          'is\n'
+          '      no reason to complicate the language with two kinds of '
+          'floating\n'
+          '      point numbers.\n'
+          '\n'
+          '   "numbers.Complex" ("complex")\n'
+          '      These represent complex numbers as a pair of machine-level\n'
+          '      double precision floating point numbers.  The same caveats '
+          'apply\n'
+          '      as for floating point numbers. The real and imaginary parts '
+          'of a\n'
+          '      complex number "z" can be retrieved through the read-only\n'
+          '      attributes "z.real" and "z.imag".\n'
+          '\n'
+          'Sequences\n'
+          '   These represent finite ordered sets indexed by non-negative\n'
+          '   numbers. The built-in function "len()" returns the number of '
+          'items\n'
+          '   of a sequence. When the length of a sequence is *n*, the index '
+          'set\n'
+          '   contains the numbers 0, 1, …, *n*-1.  Item *i* of sequence *a* '
+          'is\n'
+          '   selected by "a[i]".\n'
+          '\n'
+          '   Sequences also support slicing: "a[i:j]" selects all items with\n'
+          '   index *k* such that *i* "<=" *k* "<" *j*.  When used as an\n'
+          '   expression, a slice is a sequence of the same type.  This '
+          'implies\n'
+          '   that the index set is renumbered so that it starts at 0.\n'
+          '\n'
+          '   Some sequences also support “extended slicing” with a third '
+          '“step”\n'
+          '   parameter: "a[i:j:k]" selects all items of *a* with index *x* '
+          'where\n'
+          '   "x = i + n*k", *n* ">=" "0" and *i* "<=" *x* "<" *j*.\n'
+          '\n'
+          '   Sequences are distinguished according to their mutability:\n'
+          '\n'
+          '   Immutable sequences\n'
+          '      An object of an immutable sequence type cannot change once it '
+          'is\n'
+          '      created.  (If the object contains references to other '
+          'objects,\n'
+          '      these other objects may be mutable and may be changed; '
+          'however,\n'
+          '      the collection of objects directly referenced by an '
+          'immutable\n'
+          '      object cannot change.)\n'
+          '\n'
+          '      The following types are immutable sequences:\n'
+          '\n'
+          '      Strings\n'
+          '         A string is a sequence of values that represent Unicode '
+          'code\n'
+          '         points. All the code points in the range "U+0000 - '
+          'U+10FFFF"\n'
+          '         can be represented in a string.  Python doesn’t have a '
+          '"char"\n'
+          '         type; instead, every code point in the string is '
+          'represented\n'
+          '         as a string object with length "1".  The built-in '
+          'function\n'
+          '         "ord()" converts a code point from its string form to an\n'
+          '         integer in the range "0 - 10FFFF"; "chr()" converts an\n'
+          '         integer in the range "0 - 10FFFF" to the corresponding '
+          'length\n'
+          '         "1" string object. "str.encode()" can be used to convert '
+          'a\n'
+          '         "str" to "bytes" using the given text encoding, and\n'
+          '         "bytes.decode()" can be used to achieve the opposite.\n'
+          '\n'
+          '      Tuples\n'
+          '         The items of a tuple are arbitrary Python objects. Tuples '
+          'of\n'
+          '         two or more items are formed by comma-separated lists of\n'
+          '         expressions.  A tuple of one item (a ‘singleton’) can be\n'
+          '         formed by affixing a comma to an expression (an expression '
+          'by\n'
+          '         itself does not create a tuple, since parentheses must be\n'
+          '         usable for grouping of expressions).  An empty tuple can '
+          'be\n'
+          '         formed by an empty pair of parentheses.\n'
+          '\n'
+          '      Bytes\n'
+          '         A bytes object is an immutable array.  The items are '
+          '8-bit\n'
+          '         bytes, represented by integers in the range 0 <= x < 256.\n'
+          '         Bytes literals (like "b\'abc\'") and the built-in '
+          '"bytes()"\n'
+          '         constructor can be used to create bytes objects.  Also, '
+          'bytes\n'
+          '         objects can be decoded to strings via the "decode()" '
+          'method.\n'
+          '\n'
+          '   Mutable sequences\n'
+          '      Mutable sequences can be changed after they are created.  '
+          'The\n'
+          '      subscription and slicing notations can be used as the target '
+          'of\n'
+          '      assignment and "del" (delete) statements.\n'
+          '\n'
+          '      There are currently two intrinsic mutable sequence types:\n'
+          '\n'
+          '      Lists\n'
+          '         The items of a list are arbitrary Python objects.  Lists '
+          'are\n'
+          '         formed by placing a comma-separated list of expressions '
+          'in\n'
+          '         square brackets. (Note that there are no special cases '
+          'needed\n'
+          '         to form lists of length 0 or 1.)\n'
+          '\n'
+          '      Byte Arrays\n'
+          '         A bytearray object is a mutable array. They are created '
+          'by\n'
+          '         the built-in "bytearray()" constructor.  Aside from being\n'
+          '         mutable (and hence unhashable), byte arrays otherwise '
+          'provide\n'
+          '         the same interface and functionality as immutable "bytes"\n'
+          '         objects.\n'
+          '\n'
+          '      The extension module "array" provides an additional example '
+          'of a\n'
+          '      mutable sequence type, as does the "collections" module.\n'
+          '\n'
+          'Set types\n'
+          '   These represent unordered, finite sets of unique, immutable\n'
+          '   objects. As such, they cannot be indexed by any subscript. '
+          'However,\n'
+          '   they can be iterated over, and the built-in function "len()"\n'
+          '   returns the number of items in a set. Common uses for sets are '
+          'fast\n'
+          '   membership testing, removing duplicates from a sequence, and\n'
+          '   computing mathematical operations such as intersection, union,\n'
+          '   difference, and symmetric difference.\n'
+          '\n'
+          '   For set elements, the same immutability rules apply as for\n'
+          '   dictionary keys. Note that numeric types obey the normal rules '
+          'for\n'
+          '   numeric comparison: if two numbers compare equal (e.g., "1" and\n'
+          '   "1.0"), only one of them can be contained in a set.\n'
+          '\n'
+          '   There are currently two intrinsic set types:\n'
+          '\n'
+          '   Sets\n'
+          '      These represent a mutable set. They are created by the '
+          'built-in\n'
+          '      "set()" constructor and can be modified afterwards by '
+          'several\n'
+          '      methods, such as "add()".\n'
+          '\n'
+          '   Frozen sets\n'
+          '      These represent an immutable set.  They are created by the\n'
+          '      built-in "frozenset()" constructor.  As a frozenset is '
+          'immutable\n'
+          '      and *hashable*, it can be used again as an element of '
+          'another\n'
+          '      set, or as a dictionary key.\n'
+          '\n'
+          'Mappings\n'
+          '   These represent finite sets of objects indexed by arbitrary '
+          'index\n'
+          '   sets. The subscript notation "a[k]" selects the item indexed by '
+          '"k"\n'
+          '   from the mapping "a"; this can be used in expressions and as '
+          'the\n'
+          '   target of assignments or "del" statements. The built-in '
+          'function\n'
+          '   "len()" returns the number of items in a mapping.\n'
+          '\n'
+          '   There is currently a single intrinsic mapping type:\n'
+          '\n'
+          '   Dictionaries\n'
+          '      These represent finite sets of objects indexed by nearly\n'
+          '      arbitrary values.  The only types of values not acceptable '
+          'as\n'
+          '      keys are values containing lists or dictionaries or other\n'
+          '      mutable types that are compared by value rather than by '
+          'object\n'
+          '      identity, the reason being that the efficient implementation '
+          'of\n'
+          '      dictionaries requires a key’s hash value to remain constant.\n'
+          '      Numeric types used for keys obey the normal rules for '
+          'numeric\n'
+          '      comparison: if two numbers compare equal (e.g., "1" and '
+          '"1.0")\n'
+          '      then they can be used interchangeably to index the same\n'
+          '      dictionary entry.\n'
+          '\n'
+          '      Dictionaries are mutable; they can be created by the "{...}"\n'
+          '      notation (see section Dictionary displays).\n'
+          '\n'
+          '      The extension modules "dbm.ndbm" and "dbm.gnu" provide\n'
+          '      additional examples of mapping types, as does the '
+          '"collections"\n'
+          '      module.\n'
+          '\n'
+          'Callable types\n'
+          '   These are the types to which the function call operation (see\n'
+          '   section Calls) can be applied:\n'
+          '\n'
+          '   User-defined functions\n'
+          '      A user-defined function object is created by a function\n'
+          '      definition (see section Function definitions).  It should be\n'
+          '      called with an argument list containing the same number of '
+          'items\n'
+          '      as the function’s formal parameter list.\n'
+          '\n'
+          '      Special attributes:\n'
+          '\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | Attribute                 | Meaning                         '
+          '|             |\n'
+          '      '
+          '+===========================+=================================+=============+\n'
+          '      | "__doc__"                 | The function’s documentation    '
+          '| Writable    |\n'
+          '      |                           | string, or "None" if            '
+          '|             |\n'
+          '      |                           | unavailable; not inherited by   '
+          '|             |\n'
+          '      |                           | subclasses                      '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__name__"                | The function’s name             '
+          '| Writable    |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__qualname__"            | The function’s *qualified name* '
+          '| Writable    |\n'
+          '      |                           | New in version 3.3.             '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__module__"              | The name of the module the      '
+          '| Writable    |\n'
+          '      |                           | function was defined in, or     '
+          '|             |\n'
+          '      |                           | "None" if unavailable.          '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__defaults__"            | A tuple containing default      '
+          '| Writable    |\n'
+          '      |                           | argument values for those       '
+          '|             |\n'
+          '      |                           | arguments that have defaults,   '
+          '|             |\n'
+          '      |                           | or "None" if no arguments have  '
+          '|             |\n'
+          '      |                           | a default value                 '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__code__"                | The code object representing    '
+          '| Writable    |\n'
+          '      |                           | the compiled function body.     '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__globals__"             | A reference to the dictionary   '
+          '| Read-only   |\n'
+          '      |                           | that holds the function’s       '
+          '|             |\n'
+          '      |                           | global variables — the global   '
+          '|             |\n'
+          '      |                           | namespace of the module in      '
+          '|             |\n'
+          '      |                           | which the function was defined. '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__dict__"                | The namespace supporting        '
+          '| Writable    |\n'
+          '      |                           | arbitrary function attributes.  '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__closure__"             | "None" or a tuple of cells that '
+          '| Read-only   |\n'
+          '      |                           | contain bindings for the        '
+          '|             |\n'
+          '      |                           | function’s free variables.      '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__annotations__"         | A dict containing annotations   '
+          '| Writable    |\n'
+          '      |                           | of parameters.  The keys of the '
+          '|             |\n'
+          '      |                           | dict are the parameter names,   '
+          '|             |\n'
+          '      |                           | and "\'return\'" for the '
+          'return   |             |\n'
+          '      |                           | annotation, if provided.        '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '      | "__kwdefaults__"          | A dict containing defaults for  '
+          '| Writable    |\n'
+          '      |                           | keyword-only parameters.        '
+          '|             |\n'
+          '      '
+          '+---------------------------+---------------------------------+-------------+\n'
+          '\n'
+          '      Most of the attributes labelled “Writable” check the type of '
+          'the\n'
+          '      assigned value.\n'
+          '\n'
+          '      Function objects also support getting and setting arbitrary\n'
+          '      attributes, which can be used, for example, to attach '
+          'metadata\n'
+          '      to functions.  Regular attribute dot-notation is used to get '
+          'and\n'
+          '      set such attributes. *Note that the current implementation '
+          'only\n'
+          '      supports function attributes on user-defined functions. '
+          'Function\n'
+          '      attributes on built-in functions may be supported in the\n'
+          '      future.*\n'
+          '\n'
+          '      Additional information about a function’s definition can be\n'
+          '      retrieved from its code object; see the description of '
+          'internal\n'
+          '      types below.\n'
+          '\n'
+          '   Instance methods\n'
+          '      An instance method object combines a class, a class instance '
+          'and\n'
+          '      any callable object (normally a user-defined function).\n'
+          '\n'
+          '      Special read-only attributes: "__self__" is the class '
+          'instance\n'
+          '      object, "__func__" is the function object; "__doc__" is the\n'
+          '      method’s documentation (same as "__func__.__doc__"); '
+          '"__name__"\n'
+          '      is the method name (same as "__func__.__name__"); '
+          '"__module__"\n'
+          '      is the name of the module the method was defined in, or '
+          '"None"\n'
+          '      if unavailable.\n'
+          '\n'
+          '      Methods also support accessing (but not setting) the '
+          'arbitrary\n'
+          '      function attributes on the underlying function object.\n'
+          '\n'
+          '      User-defined method objects may be created when getting an\n'
+          '      attribute of a class (perhaps via an instance of that class), '
+          'if\n'
+          '      that attribute is a user-defined function object or a class\n'
+          '      method object.\n'
+          '\n'
+          '      When an instance method object is created by retrieving a '
+          'user-\n'
+          '      defined function object from a class via one of its '
+          'instances,\n'
+          '      its "__self__" attribute is the instance, and the method '
+          'object\n'
+          '      is said to be bound.  The new method’s "__func__" attribute '
+          'is\n'
+          '      the original function object.\n'
+          '\n'
+          '      When a user-defined method object is created by retrieving\n'
+          '      another method object from a class or instance, the behaviour '
+          'is\n'
+          '      the same as for a function object, except that the '
+          '"__func__"\n'
+          '      attribute of the new instance is not the original method '
+          'object\n'
+          '      but its "__func__" attribute.\n'
+          '\n'
+          '      When an instance method object is created by retrieving a '
+          'class\n'
+          '      method object from a class or instance, its "__self__" '
+          'attribute\n'
+          '      is the class itself, and its "__func__" attribute is the\n'
+          '      function object underlying the class method.\n'
+          '\n'
+          '      When an instance method object is called, the underlying\n'
+          '      function ("__func__") is called, inserting the class '
+          'instance\n'
+          '      ("__self__") in front of the argument list.  For instance, '
+          'when\n'
+          '      "C" is a class which contains a definition for a function '
+          '"f()",\n'
+          '      and "x" is an instance of "C", calling "x.f(1)" is equivalent '
+          'to\n'
+          '      calling "C.f(x, 1)".\n'
+          '\n'
+          '      When an instance method object is derived from a class '
+          'method\n'
+          '      object, the “class instance” stored in "__self__" will '
+          'actually\n'
+          '      be the class itself, so that calling either "x.f(1)" or '
+          '"C.f(1)"\n'
+          '      is equivalent to calling "f(C,1)" where "f" is the '
+          'underlying\n'
+          '      function.\n'
+          '\n'
+          '      Note that the transformation from function object to '
+          'instance\n'
+          '      method object happens each time the attribute is retrieved '
+          'from\n'
+          '      the instance.  In some cases, a fruitful optimization is to\n'
+          '      assign the attribute to a local variable and call that local\n'
+          '      variable. Also notice that this transformation only happens '
+          'for\n'
+          '      user-defined functions; other callable objects (and all non-\n'
+          '      callable objects) are retrieved without transformation.  It '
+          'is\n'
+          '      also important to note that user-defined functions which are\n'
+          '      attributes of a class instance are not converted to bound\n'
+          '      methods; this *only* happens when the function is an '
+          'attribute\n'
+          '      of the class.\n'
+          '\n'
+          '   Generator functions\n'
+          '      A function or method which uses the "yield" statement (see\n'
+          '      section The yield statement) is called a *generator '
+          'function*.\n'
+          '      Such a function, when called, always returns an iterator '
+          'object\n'
+          '      which can be used to execute the body of the function:  '
+          'calling\n'
+          '      the iterator’s "iterator.__next__()" method will cause the\n'
+          '      function to execute until it provides a value using the '
+          '"yield"\n'
+          '      statement.  When the function executes a "return" statement '
+          'or\n'
+          '      falls off the end, a "StopIteration" exception is raised and '
+          'the\n'
+          '      iterator will have reached the end of the set of values to '
+          'be\n'
+          '      returned.\n'
+          '\n'
+          '   Coroutine functions\n'
+          '      A function or method which is defined using "async def" is\n'
+          '      called a *coroutine function*.  Such a function, when '
+          'called,\n'
+          '      returns a *coroutine* object.  It may contain "await"\n'
+          '      expressions, as well as "async with" and "async for" '
+          'statements.\n'
+          '      See also the Coroutine Objects section.\n'
+          '\n'
+          '   Asynchronous generator functions\n'
+          '      A function or method which is defined using "async def" and\n'
+          '      which uses the "yield" statement is called a *asynchronous\n'
+          '      generator function*.  Such a function, when called, returns '
+          'an\n'
+          '      asynchronous iterator object which can be used in an "async '
+          'for"\n'
+          '      statement to execute the body of the function.\n'
+          '\n'
+          '      Calling the asynchronous iterator’s "aiterator.__anext__()"\n'
+          '      method will return an *awaitable* which when awaited will\n'
+          '      execute until it provides a value using the "yield" '
+          'expression.\n'
+          '      When the function executes an empty "return" statement or '
+          'falls\n'
+          '      off the end, a "StopAsyncIteration" exception is raised and '
+          'the\n'
+          '      asynchronous iterator will have reached the end of the set '
+          'of\n'
+          '      values to be yielded.\n'
+          '\n'
+          '   Built-in functions\n'
+          '      A built-in function object is a wrapper around a C function.\n'
+          '      Examples of built-in functions are "len()" and "math.sin()"\n'
+          '      ("math" is a standard built-in module). The number and type '
+          'of\n'
+          '      the arguments are determined by the C function. Special '
+          'read-\n'
+          '      only attributes: "__doc__" is the function’s documentation\n'
+          '      string, or "None" if unavailable; "__name__" is the '
+          'function’s\n'
+          '      name; "__self__" is set to "None" (but see the next item);\n'
+          '      "__module__" is the name of the module the function was '
+          'defined\n'
+          '      in or "None" if unavailable.\n'
+          '\n'
+          '   Built-in methods\n'
+          '      This is really a different disguise of a built-in function, '
+          'this\n'
+          '      time containing an object passed to the C function as an\n'
+          '      implicit extra argument.  An example of a built-in method is\n'
+          '      "alist.append()", assuming *alist* is a list object. In this\n'
+          '      case, the special read-only attribute "__self__" is set to '
+          'the\n'
+          '      object denoted by *alist*.\n'
+          '\n'
+          '   Classes\n'
+          '      Classes are callable.  These objects normally act as '
+          'factories\n'
+          '      for new instances of themselves, but variations are possible '
+          'for\n'
+          '      class types that override "__new__()".  The arguments of the\n'
+          '      call are passed to "__new__()" and, in the typical case, to\n'
+          '      "__init__()" to initialize the new instance.\n'
+          '\n'
+          '   Class Instances\n'
+          '      Instances of arbitrary classes can be made callable by '
+          'defining\n'
+          '      a "__call__()" method in their class.\n'
+          '\n'
+          'Modules\n'
+          '   Modules are a basic organizational unit of Python code, and are\n'
+          '   created by the import system as invoked either by the "import"\n'
+          '   statement (see "import"), or by calling functions such as\n'
+          '   "importlib.import_module()" and built-in "__import__()".  A '
+          'module\n'
+          '   object has a namespace implemented by a dictionary object (this '
+          'is\n'
+          '   the dictionary referenced by the "__globals__" attribute of\n'
+          '   functions defined in the module).  Attribute references are\n'
+          '   translated to lookups in this dictionary, e.g., "m.x" is '
+          'equivalent\n'
+          '   to "m.__dict__["x"]". A module object does not contain the code\n'
+          '   object used to initialize the module (since it isn’t needed '
+          'once\n'
+          '   the initialization is done).\n'
+          '\n'
+          '   Attribute assignment updates the module’s namespace dictionary,\n'
+          '   e.g., "m.x = 1" is equivalent to "m.__dict__["x"] = 1".\n'
+          '\n'
+          '   Predefined (writable) attributes: "__name__" is the module’s '
+          'name;\n'
+          '   "__doc__" is the module’s documentation string, or "None" if\n'
+          '   unavailable; "__annotations__" (optional) is a dictionary\n'
+          '   containing *variable annotations* collected during module body\n'
+          '   execution; "__file__" is the pathname of the file from which '
+          'the\n'
+          '   module was loaded, if it was loaded from a file. The "__file__"\n'
+          '   attribute may be missing for certain types of modules, such as '
+          'C\n'
+          '   modules that are statically linked into the interpreter; for\n'
+          '   extension modules loaded dynamically from a shared library, it '
+          'is\n'
+          '   the pathname of the shared library file.\n'
+          '\n'
+          '   Special read-only attribute: "__dict__" is the module’s '
+          'namespace\n'
+          '   as a dictionary object.\n'
+          '\n'
+          '   **CPython implementation detail:** Because of the way CPython\n'
+          '   clears module dictionaries, the module dictionary will be '
+          'cleared\n'
+          '   when the module falls out of scope even if the dictionary still '
+          'has\n'
+          '   live references.  To avoid this, copy the dictionary or keep '
+          'the\n'
+          '   module around while using its dictionary directly.\n'
+          '\n'
+          'Custom classes\n'
+          '   Custom class types are typically created by class definitions '
+          '(see\n'
+          '   section Class definitions).  A class has a namespace implemented '
+          'by\n'
+          '   a dictionary object. Class attribute references are translated '
+          'to\n'
+          '   lookups in this dictionary, e.g., "C.x" is translated to\n'
+          '   "C.__dict__["x"]" (although there are a number of hooks which '
+          'allow\n'
+          '   for other means of locating attributes). When the attribute name '
+          'is\n'
+          '   not found there, the attribute search continues in the base\n'
+          '   classes. This search of the base classes uses the C3 method\n'
+          '   resolution order which behaves correctly even in the presence '
+          'of\n'
+          '   ‘diamond’ inheritance structures where there are multiple\n'
+          '   inheritance paths leading back to a common ancestor. Additional\n'
+          '   details on the C3 MRO used by Python can be found in the\n'
+          '   documentation accompanying the 2.3 release at\n'
+          '   https://www.python.org/download/releases/2.3/mro/.\n'
+          '\n'
+          '   When a class attribute reference (for class "C", say) would '
+          'yield a\n'
+          '   class method object, it is transformed into an instance method\n'
+          '   object whose "__self__" attribute is "C".  When it would yield '
+          'a\n'
+          '   static method object, it is transformed into the object wrapped '
+          'by\n'
+          '   the static method object. See section Implementing Descriptors '
+          'for\n'
+          '   another way in which attributes retrieved from a class may '
+          'differ\n'
+          '   from those actually contained in its "__dict__".\n'
+          '\n'
+          '   Class attribute assignments update the class’s dictionary, '
+          'never\n'
+          '   the dictionary of a base class.\n'
+          '\n'
+          '   A class object can be called (see above) to yield a class '
+          'instance\n'
+          '   (see below).\n'
+          '\n'
+          '   Special attributes: "__name__" is the class name; "__module__" '
+          'is\n'
+          '   the module name in which the class was defined; "__dict__" is '
+          'the\n'
+          '   dictionary containing the class’s namespace; "__bases__" is a '
+          'tuple\n'
+          '   containing the base classes, in the order of their occurrence '
+          'in\n'
+          '   the base class list; "__doc__" is the class’s documentation '
+          'string,\n'
+          '   or "None" if undefined; "__annotations__" (optional) is a\n'
+          '   dictionary containing *variable annotations* collected during '
+          'class\n'
+          '   body execution.\n'
+          '\n'
+          'Class instances\n'
+          '   A class instance is created by calling a class object (see '
+          'above).\n'
+          '   A class instance has a namespace implemented as a dictionary '
+          'which\n'
+          '   is the first place in which attribute references are searched.\n'
+          '   When an attribute is not found there, and the instance’s class '
+          'has\n'
+          '   an attribute by that name, the search continues with the class\n'
+          '   attributes.  If a class attribute is found that is a '
+          'user-defined\n'
+          '   function object, it is transformed into an instance method '
+          'object\n'
+          '   whose "__self__" attribute is the instance.  Static method and\n'
+          '   class method objects are also transformed; see above under\n'
+          '   “Classes”.  See section Implementing Descriptors for another way '
+          'in\n'
+          '   which attributes of a class retrieved via its instances may '
+          'differ\n'
+          '   from the objects actually stored in the class’s "__dict__".  If '
+          'no\n'
+          '   class attribute is found, and the object’s class has a\n'
+          '   "__getattr__()" method, that is called to satisfy the lookup.\n'
+          '\n'
+          '   Attribute assignments and deletions update the instance’s\n'
+          '   dictionary, never a class’s dictionary.  If the class has a\n'
+          '   "__setattr__()" or "__delattr__()" method, this is called '
+          'instead\n'
+          '   of updating the instance dictionary directly.\n'
+          '\n'
+          '   Class instances can pretend to be numbers, sequences, or '
+          'mappings\n'
+          '   if they have methods with certain special names.  See section\n'
+          '   Special method names.\n'
+          '\n'
+          '   Special attributes: "__dict__" is the attribute dictionary;\n'
+          '   "__class__" is the instance’s class.\n'
+          '\n'
+          'I/O objects (also known as file objects)\n'
+          '   A *file object* represents an open file.  Various shortcuts are\n'
+          '   available to create file objects: the "open()" built-in '
+          'function,\n'
+          '   and also "os.popen()", "os.fdopen()", and the "makefile()" '
+          'method\n'
+          '   of socket objects (and perhaps by other functions or methods\n'
+          '   provided by extension modules).\n'
+          '\n'
+          '   The objects "sys.stdin", "sys.stdout" and "sys.stderr" are\n'
+          '   initialized to file objects corresponding to the interpreter’s\n'
+          '   standard input, output and error streams; they are all open in '
+          'text\n'
+          '   mode and therefore follow the interface defined by the\n'
+          '   "io.TextIOBase" abstract class.\n'
+          '\n'
+          'Internal types\n'
+          '   A few types used internally by the interpreter are exposed to '
+          'the\n'
+          '   user. Their definitions may change with future versions of the\n'
+          '   interpreter, but they are mentioned here for completeness.\n'
+          '\n'
+          '   Code objects\n'
+          '      Code objects represent *byte-compiled* executable Python '
+          'code,\n'
+          '      or *bytecode*. The difference between a code object and a\n'
+          '      function object is that the function object contains an '
+          'explicit\n'
+          '      reference to the function’s globals (the module in which it '
+          'was\n'
+          '      defined), while a code object contains no context; also the\n'
+          '      default argument values are stored in the function object, '
+          'not\n'
+          '      in the code object (because they represent values calculated '
+          'at\n'
+          '      run-time).  Unlike function objects, code objects are '
+          'immutable\n'
+          '      and contain no references (directly or indirectly) to '
+          'mutable\n'
+          '      objects.\n'
+          '\n'
+          '      Special read-only attributes: "co_name" gives the function '
+          'name;\n'
+          '      "co_argcount" is the number of positional arguments '
+          '(including\n'
+          '      arguments with default values); "co_nlocals" is the number '
+          'of\n'
+          '      local variables used by the function (including arguments);\n'
+          '      "co_varnames" is a tuple containing the names of the local\n'
+          '      variables (starting with the argument names); "co_cellvars" '
+          'is a\n'
+          '      tuple containing the names of local variables that are\n'
+          '      referenced by nested functions; "co_freevars" is a tuple\n'
+          '      containing the names of free variables; "co_code" is a '
+          'string\n'
+          '      representing the sequence of bytecode instructions; '
+          '"co_consts"\n'
+          '      is a tuple containing the literals used by the bytecode;\n'
+          '      "co_names" is a tuple containing the names used by the '
+          'bytecode;\n'
+          '      "co_filename" is the filename from which the code was '
+          'compiled;\n'
+          '      "co_firstlineno" is the first line number of the function;\n'
+          '      "co_lnotab" is a string encoding the mapping from bytecode\n'
+          '      offsets to line numbers (for details see the source code of '
+          'the\n'
+          '      interpreter); "co_stacksize" is the required stack size\n'
+          '      (including local variables); "co_flags" is an integer '
+          'encoding a\n'
+          '      number of flags for the interpreter.\n'
+          '\n'
+          '      The following flag bits are defined for "co_flags": bit '
+          '"0x04"\n'
+          '      is set if the function uses the "*arguments" syntax to accept '
+          'an\n'
+          '      arbitrary number of positional arguments; bit "0x08" is set '
+          'if\n'
+          '      the function uses the "**keywords" syntax to accept '
+          'arbitrary\n'
+          '      keyword arguments; bit "0x20" is set if the function is a\n'
+          '      generator.\n'
+          '\n'
+          '      Future feature declarations ("from __future__ import '
+          'division")\n'
+          '      also use bits in "co_flags" to indicate whether a code '
+          'object\n'
+          '      was compiled with a particular feature enabled: bit "0x2000" '
+          'is\n'
+          '      set if the function was compiled with future division '
+          'enabled;\n'
+          '      bits "0x10" and "0x1000" were used in earlier versions of\n'
+          '      Python.\n'
+          '\n'
+          '      Other bits in "co_flags" are reserved for internal use.\n'
+          '\n'
+          '      If a code object represents a function, the first item in\n'
+          '      "co_consts" is the documentation string of the function, or\n'
+          '      "None" if undefined.\n'
+          '\n'
+          '   Frame objects\n'
+          '      Frame objects represent execution frames.  They may occur in\n'
+          '      traceback objects (see below).\n'
+          '\n'
+          '      Special read-only attributes: "f_back" is to the previous '
+          'stack\n'
+          '      frame (towards the caller), or "None" if this is the bottom\n'
+          '      stack frame; "f_code" is the code object being executed in '
+          'this\n'
+          '      frame; "f_locals" is the dictionary used to look up local\n'
+          '      variables; "f_globals" is used for global variables;\n'
+          '      "f_builtins" is used for built-in (intrinsic) names; '
+          '"f_lasti"\n'
+          '      gives the precise instruction (this is an index into the\n'
+          '      bytecode string of the code object).\n'
+          '\n'
+          '      Special writable attributes: "f_trace", if not "None", is a\n'
+          '      function called at the start of each source code line (this '
+          'is\n'
+          '      used by the debugger); "f_lineno" is the current line number '
+          'of\n'
+          '      the frame — writing to this from within a trace function '
+          'jumps\n'
+          '      to the given line (only for the bottom-most frame).  A '
+          'debugger\n'
+          '      can implement a Jump command (aka Set Next Statement) by '
+          'writing\n'
+          '      to f_lineno.\n'
+          '\n'
+          '      Frame objects support one method:\n'
+          '\n'
+          '      frame.clear()\n'
+          '\n'
+          '         This method clears all references to local variables held '
+          'by\n'
+          '         the frame.  Also, if the frame belonged to a generator, '
+          'the\n'
+          '         generator is finalized.  This helps break reference '
+          'cycles\n'
+          '         involving frame objects (for example when catching an\n'
+          '         exception and storing its traceback for later use).\n'
+          '\n'
+          '         "RuntimeError" is raised if the frame is currently '
+          'executing.\n'
+          '\n'
+          '         New in version 3.4.\n'
+          '\n'
+          '   Traceback objects\n'
+          '      Traceback objects represent a stack trace of an exception.  '
+          'A\n'
+          '      traceback object is created when an exception occurs.  When '
+          'the\n'
+          '      search for an exception handler unwinds the execution stack, '
+          'at\n'
+          '      each unwound level a traceback object is inserted in front '
+          'of\n'
+          '      the current traceback.  When an exception handler is '
+          'entered,\n'
+          '      the stack trace is made available to the program. (See '
+          'section\n'
+          '      The try statement.) It is accessible as the third item of '
+          'the\n'
+          '      tuple returned by "sys.exc_info()". When the program contains '
+          'no\n'
+          '      suitable handler, the stack trace is written (nicely '
+          'formatted)\n'
+          '      to the standard error stream; if the interpreter is '
+          'interactive,\n'
+          '      it is also made available to the user as '
+          '"sys.last_traceback".\n'
+          '\n'
+          '      Special read-only attributes: "tb_next" is the next level in '
+          'the\n'
+          '      stack trace (towards the frame where the exception occurred), '
+          'or\n'
+          '      "None" if there is no next level; "tb_frame" points to the\n'
+          '      execution frame of the current level; "tb_lineno" gives the '
+          'line\n'
+          '      number where the exception occurred; "tb_lasti" indicates '
+          'the\n'
+          '      precise instruction.  The line number and last instruction '
+          'in\n'
+          '      the traceback may differ from the line number of its frame\n'
+          '      object if the exception occurred in a "try" statement with '
+          'no\n'
+          '      matching except clause or with a finally clause.\n'
+          '\n'
+          '   Slice objects\n'
+          '      Slice objects are used to represent slices for '
+          '"__getitem__()"\n'
+          '      methods.  They are also created by the built-in "slice()"\n'
+          '      function.\n'
+          '\n'
+          '      Special read-only attributes: "start" is the lower bound; '
+          '"stop"\n'
+          '      is the upper bound; "step" is the step value; each is "None" '
+          'if\n'
+          '      omitted.  These attributes can have any type.\n'
+          '\n'
+          '      Slice objects support one method:\n'
+          '\n'
+          '      slice.indices(self, length)\n'
+          '\n'
+          '         This method takes a single integer argument *length* and\n'
+          '         computes information about the slice that the slice '
+          'object\n'
+          '         would describe if applied to a sequence of *length* '
+          'items.\n'
+          '         It returns a tuple of three integers; respectively these '
+          'are\n'
+          '         the *start* and *stop* indices and the *step* or stride\n'
+          '         length of the slice. Missing or out-of-bounds indices are\n'
+          '         handled in a manner consistent with regular slices.\n'
+          '\n'
+          '   Static method objects\n'
+          '      Static method objects provide a way of defeating the\n'
+          '      transformation of function objects to method objects '
+          'described\n'
+          '      above. A static method object is a wrapper around any other\n'
+          '      object, usually a user-defined method object. When a static\n'
+          '      method object is retrieved from a class or a class instance, '
+          'the\n'
+          '      object actually returned is the wrapped object, which is not\n'
+          '      subject to any further transformation. Static method objects '
+          'are\n'
+          '      not themselves callable, although the objects they wrap '
+          'usually\n'
+          '      are. Static method objects are created by the built-in\n'
+          '      "staticmethod()" constructor.\n'
+          '\n'
+          '   Class method objects\n'
+          '      A class method object, like a static method object, is a '
+          'wrapper\n'
+          '      around another object that alters the way in which that '
+          'object\n'
+          '      is retrieved from classes and class instances. The behaviour '
+          'of\n'
+          '      class method objects upon such retrieval is described above,\n'
+          '      under “User-defined methods”. Class method objects are '
+          'created\n'
+          '      by the built-in "classmethod()" constructor.\n',
+ 'typesfunctions': 'Functions\n'
+                   '*********\n'
+                   '\n'
+                   'Function objects are created by function definitions.  The '
+                   'only\n'
+                   'operation on a function object is to call it: '
+                   '"func(argument-list)".\n'
+                   '\n'
+                   'There are really two flavors of function objects: built-in '
+                   'functions\n'
+                   'and user-defined functions.  Both support the same '
+                   'operation (to call\n'
+                   'the function), but the implementation is different, hence '
+                   'the\n'
+                   'different object types.\n'
+                   '\n'
+                   'See Function definitions for more information.\n',
+ 'typesmapping': 'Mapping Types — "dict"\n'
+                 '**********************\n'
+                 '\n'
+                 'A *mapping* object maps *hashable* values to arbitrary '
+                 'objects.\n'
+                 'Mappings are mutable objects.  There is currently only one '
+                 'standard\n'
+                 'mapping type, the *dictionary*.  (For other containers see '
+                 'the built-\n'
+                 'in "list", "set", and "tuple" classes, and the "collections" '
+                 'module.)\n'
+                 '\n'
+                 'A dictionary’s keys are *almost* arbitrary values.  Values '
+                 'that are\n'
+                 'not *hashable*, that is, values containing lists, '
+                 'dictionaries or\n'
+                 'other mutable types (that are compared by value rather than '
+                 'by object\n'
+                 'identity) may not be used as keys.  Numeric types used for '
+                 'keys obey\n'
+                 'the normal rules for numeric comparison: if two numbers '
+                 'compare equal\n'
+                 '(such as "1" and "1.0") then they can be used '
+                 'interchangeably to index\n'
+                 'the same dictionary entry.  (Note however, that since '
+                 'computers store\n'
+                 'floating-point numbers as approximations it is usually '
+                 'unwise to use\n'
+                 'them as dictionary keys.)\n'
+                 '\n'
+                 'Dictionaries can be created by placing a comma-separated '
+                 'list of "key:\n'
+                 'value" pairs within braces, for example: "{\'jack\': 4098, '
+                 "'sjoerd':\n"
+                 '4127}" or "{4098: \'jack\', 4127: \'sjoerd\'}", or by the '
+                 '"dict"\n'
+                 'constructor.\n'
+                 '\n'
+                 'class dict(**kwarg)\n'
+                 'class dict(mapping, **kwarg)\n'
+                 'class dict(iterable, **kwarg)\n'
+                 '\n'
+                 '   Return a new dictionary initialized from an optional '
+                 'positional\n'
+                 '   argument and a possibly empty set of keyword arguments.\n'
+                 '\n'
+                 '   If no positional argument is given, an empty dictionary '
+                 'is created.\n'
+                 '   If a positional argument is given and it is a mapping '
+                 'object, a\n'
+                 '   dictionary is created with the same key-value pairs as '
+                 'the mapping\n'
+                 '   object.  Otherwise, the positional argument must be an '
+                 '*iterable*\n'
+                 '   object.  Each item in the iterable must itself be an '
+                 'iterable with\n'
+                 '   exactly two objects.  The first object of each item '
+                 'becomes a key\n'
+                 '   in the new dictionary, and the second object the '
+                 'corresponding\n'
+                 '   value.  If a key occurs more than once, the last value '
+                 'for that key\n'
+                 '   becomes the corresponding value in the new dictionary.\n'
+                 '\n'
+                 '   If keyword arguments are given, the keyword arguments and '
+                 'their\n'
+                 '   values are added to the dictionary created from the '
+                 'positional\n'
+                 '   argument.  If a key being added is already present, the '
+                 'value from\n'
+                 '   the keyword argument replaces the value from the '
+                 'positional\n'
+                 '   argument.\n'
+                 '\n'
+                 '   To illustrate, the following examples all return a '
+                 'dictionary equal\n'
+                 '   to "{"one": 1, "two": 2, "three": 3}":\n'
+                 '\n'
+                 '      >>> a = dict(one=1, two=2, three=3)\n'
+                 "      >>> b = {'one': 1, 'two': 2, 'three': 3}\n"
+                 "      >>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))\n"
+                 "      >>> d = dict([('two', 2), ('one', 1), ('three', 3)])\n"
+                 "      >>> e = dict({'three': 3, 'one': 1, 'two': 2})\n"
+                 '      >>> a == b == c == d == e\n'
+                 '      True\n'
+                 '\n'
+                 '   Providing keyword arguments as in the first example only '
+                 'works for\n'
+                 '   keys that are valid Python identifiers.  Otherwise, any '
+                 'valid keys\n'
+                 '   can be used.\n'
+                 '\n'
+                 '   These are the operations that dictionaries support (and '
+                 'therefore,\n'
+                 '   custom mapping types should support too):\n'
+                 '\n'
+                 '   len(d)\n'
+                 '\n'
+                 '      Return the number of items in the dictionary *d*.\n'
+                 '\n'
+                 '   d[key]\n'
+                 '\n'
+                 '      Return the item of *d* with key *key*.  Raises a '
+                 '"KeyError" if\n'
+                 '      *key* is not in the map.\n'
+                 '\n'
+                 '      If a subclass of dict defines a method "__missing__()" '
+                 'and *key*\n'
+                 '      is not present, the "d[key]" operation calls that '
+                 'method with\n'
+                 '      the key *key* as argument.  The "d[key]" operation '
+                 'then returns\n'
+                 '      or raises whatever is returned or raised by the\n'
+                 '      "__missing__(key)" call. No other operations or '
+                 'methods invoke\n'
+                 '      "__missing__()". If "__missing__()" is not defined, '
+                 '"KeyError"\n'
+                 '      is raised. "__missing__()" must be a method; it cannot '
+                 'be an\n'
+                 '      instance variable:\n'
+                 '\n'
+                 '         >>> class Counter(dict):\n'
+                 '         ...     def __missing__(self, key):\n'
+                 '         ...         return 0\n'
+                 '         >>> c = Counter()\n'
+                 "         >>> c['red']\n"
+                 '         0\n'
+                 "         >>> c['red'] += 1\n"
+                 "         >>> c['red']\n"
+                 '         1\n'
+                 '\n'
+                 '      The example above shows part of the implementation of\n'
+                 '      "collections.Counter".  A different "__missing__" '
+                 'method is used\n'
+                 '      by "collections.defaultdict".\n'
+                 '\n'
+                 '   d[key] = value\n'
+                 '\n'
+                 '      Set "d[key]" to *value*.\n'
+                 '\n'
+                 '   del d[key]\n'
+                 '\n'
+                 '      Remove "d[key]" from *d*.  Raises a "KeyError" if '
+                 '*key* is not\n'
+                 '      in the map.\n'
+                 '\n'
+                 '   key in d\n'
+                 '\n'
+                 '      Return "True" if *d* has a key *key*, else "False".\n'
+                 '\n'
+                 '   key not in d\n'
+                 '\n'
+                 '      Equivalent to "not key in d".\n'
+                 '\n'
+                 '   iter(d)\n'
+                 '\n'
+                 '      Return an iterator over the keys of the dictionary.  '
+                 'This is a\n'
+                 '      shortcut for "iter(d.keys())".\n'
+                 '\n'
+                 '   clear()\n'
+                 '\n'
+                 '      Remove all items from the dictionary.\n'
+                 '\n'
+                 '   copy()\n'
+                 '\n'
+                 '      Return a shallow copy of the dictionary.\n'
+                 '\n'
+                 '   classmethod fromkeys(seq[, value])\n'
+                 '\n'
+                 '      Create a new dictionary with keys from *seq* and '
+                 'values set to\n'
+                 '      *value*.\n'
+                 '\n'
+                 '      "fromkeys()" is a class method that returns a new '
+                 'dictionary.\n'
+                 '      *value* defaults to "None".\n'
+                 '\n'
+                 '   get(key[, default])\n'
+                 '\n'
+                 '      Return the value for *key* if *key* is in the '
+                 'dictionary, else\n'
+                 '      *default*. If *default* is not given, it defaults to '
+                 '"None", so\n'
+                 '      that this method never raises a "KeyError".\n'
+                 '\n'
+                 '   items()\n'
+                 '\n'
+                 '      Return a new view of the dictionary’s items ("(key, '
+                 'value)"\n'
+                 '      pairs). See the documentation of view objects.\n'
+                 '\n'
+                 '   keys()\n'
+                 '\n'
+                 '      Return a new view of the dictionary’s keys.  See the\n'
+                 '      documentation of view objects.\n'
+                 '\n'
+                 '   pop(key[, default])\n'
+                 '\n'
+                 '      If *key* is in the dictionary, remove it and return '
+                 'its value,\n'
+                 '      else return *default*.  If *default* is not given and '
+                 '*key* is\n'
+                 '      not in the dictionary, a "KeyError" is raised.\n'
+                 '\n'
+                 '   popitem()\n'
+                 '\n'
+                 '      Remove and return an arbitrary "(key, value)" pair '
+                 'from the\n'
+                 '      dictionary.\n'
+                 '\n'
+                 '      "popitem()" is useful to destructively iterate over a\n'
+                 '      dictionary, as often used in set algorithms.  If the '
+                 'dictionary\n'
+                 '      is empty, calling "popitem()" raises a "KeyError".\n'
+                 '\n'
+                 '   setdefault(key[, default])\n'
+                 '\n'
+                 '      If *key* is in the dictionary, return its value.  If '
+                 'not, insert\n'
+                 '      *key* with a value of *default* and return *default*.  '
+                 '*default*\n'
+                 '      defaults to "None".\n'
+                 '\n'
+                 '   update([other])\n'
+                 '\n'
+                 '      Update the dictionary with the key/value pairs from '
+                 '*other*,\n'
+                 '      overwriting existing keys.  Return "None".\n'
+                 '\n'
+                 '      "update()" accepts either another dictionary object or '
+                 'an\n'
+                 '      iterable of key/value pairs (as tuples or other '
+                 'iterables of\n'
+                 '      length two).  If keyword arguments are specified, the '
+                 'dictionary\n'
+                 '      is then updated with those key/value pairs: '
+                 '"d.update(red=1,\n'
+                 '      blue=2)".\n'
+                 '\n'
+                 '   values()\n'
+                 '\n'
+                 '      Return a new view of the dictionary’s values.  See '
+                 'the\n'
+                 '      documentation of view objects.\n'
+                 '\n'
+                 '   Dictionaries compare equal if and only if they have the '
+                 'same "(key,\n'
+                 '   value)" pairs. Order comparisons (‘<’, ‘<=’, ‘>=’, ‘>’) '
+                 'raise\n'
+                 '   "TypeError".\n'
+                 '\n'
+                 'See also: "types.MappingProxyType" can be used to create a '
+                 'read-only\n'
+                 '  view of a "dict".\n'
+                 '\n'
+                 '\n'
+                 'Dictionary view objects\n'
+                 '=======================\n'
+                 '\n'
+                 'The objects returned by "dict.keys()", "dict.values()" and\n'
+                 '"dict.items()" are *view objects*.  They provide a dynamic '
+                 'view on the\n'
+                 'dictionary’s entries, which means that when the dictionary '
+                 'changes,\n'
+                 'the view reflects these changes.\n'
+                 '\n'
+                 'Dictionary views can be iterated over to yield their '
+                 'respective data,\n'
+                 'and support membership tests:\n'
+                 '\n'
+                 'len(dictview)\n'
+                 '\n'
+                 '   Return the number of entries in the dictionary.\n'
+                 '\n'
+                 'iter(dictview)\n'
+                 '\n'
+                 '   Return an iterator over the keys, values or items '
+                 '(represented as\n'
+                 '   tuples of "(key, value)") in the dictionary.\n'
+                 '\n'
+                 '   Keys and values are iterated over in an arbitrary order '
+                 'which is\n'
+                 '   non-random, varies across Python implementations, and '
+                 'depends on\n'
+                 '   the dictionary’s history of insertions and deletions. If '
+                 'keys,\n'
+                 '   values and items views are iterated over with no '
+                 'intervening\n'
+                 '   modifications to the dictionary, the order of items will '
+                 'directly\n'
+                 '   correspond.  This allows the creation of "(value, key)" '
+                 'pairs using\n'
+                 '   "zip()": "pairs = zip(d.values(), d.keys())".  Another '
+                 'way to\n'
+                 '   create the same list is "pairs = [(v, k) for (k, v) in '
+                 'd.items()]".\n'
+                 '\n'
+                 '   Iterating views while adding or deleting entries in the '
+                 'dictionary\n'
+                 '   may raise a "RuntimeError" or fail to iterate over all '
+                 'entries.\n'
+                 '\n'
+                 'x in dictview\n'
+                 '\n'
+                 '   Return "True" if *x* is in the underlying dictionary’s '
+                 'keys, values\n'
+                 '   or items (in the latter case, *x* should be a "(key, '
+                 'value)"\n'
+                 '   tuple).\n'
+                 '\n'
+                 'Keys views are set-like since their entries are unique and '
+                 'hashable.\n'
+                 'If all values are hashable, so that "(key, value)" pairs are '
+                 'unique\n'
+                 'and hashable, then the items view is also set-like.  (Values '
+                 'views are\n'
+                 'not treated as set-like since the entries are generally not '
+                 'unique.)\n'
+                 'For set-like views, all of the operations defined for the '
+                 'abstract\n'
+                 'base class "collections.abc.Set" are available (for example, '
+                 '"==",\n'
+                 '"<", or "^").\n'
+                 '\n'
+                 'An example of dictionary view usage:\n'
+                 '\n'
+                 "   >>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, "
+                 "'spam': 500}\n"
+                 '   >>> keys = dishes.keys()\n'
+                 '   >>> values = dishes.values()\n'
+                 '\n'
+                 '   >>> # iteration\n'
+                 '   >>> n = 0\n'
+                 '   >>> for val in values:\n'
+                 '   ...     n += val\n'
+                 '   >>> print(n)\n'
+                 '   504\n'
+                 '\n'
+                 '   >>> # keys and values are iterated over in the same '
+                 'order\n'
+                 '   >>> list(keys)\n'
+                 "   ['eggs', 'bacon', 'sausage', 'spam']\n"
+                 '   >>> list(values)\n'
+                 '   [2, 1, 1, 500]\n'
+                 '\n'
+                 '   >>> # view objects are dynamic and reflect dict changes\n'
+                 "   >>> del dishes['eggs']\n"
+                 "   >>> del dishes['sausage']\n"
+                 '   >>> list(keys)\n'
+                 "   ['spam', 'bacon']\n"
+                 '\n'
+                 '   >>> # set operations\n'
+                 "   >>> keys & {'eggs', 'bacon', 'salad'}\n"
+                 "   {'bacon'}\n"
+                 "   >>> keys ^ {'sausage', 'juice'}\n"
+                 "   {'juice', 'sausage', 'bacon', 'spam'}\n",
+ 'typesmethods': 'Methods\n'
+                 '*******\n'
+                 '\n'
+                 'Methods are functions that are called using the attribute '
+                 'notation.\n'
+                 'There are two flavors: built-in methods (such as "append()" '
+                 'on lists)\n'
+                 'and class instance methods.  Built-in methods are described '
+                 'with the\n'
+                 'types that support them.\n'
+                 '\n'
+                 'If you access a method (a function defined in a class '
+                 'namespace)\n'
+                 'through an instance, you get a special object: a *bound '
+                 'method* (also\n'
+                 'called *instance method*) object. When called, it will add '
+                 'the "self"\n'
+                 'argument to the argument list.  Bound methods have two '
+                 'special read-\n'
+                 'only attributes: "m.__self__" is the object on which the '
+                 'method\n'
+                 'operates, and "m.__func__" is the function implementing the '
+                 'method.\n'
+                 'Calling "m(arg-1, arg-2, ..., arg-n)" is completely '
+                 'equivalent to\n'
+                 'calling "m.__func__(m.__self__, arg-1, arg-2, ..., arg-n)".\n'
+                 '\n'
+                 'Like function objects, bound method objects support getting '
+                 'arbitrary\n'
+                 'attributes.  However, since method attributes are actually '
+                 'stored on\n'
+                 'the underlying function object ("meth.__func__"), setting '
+                 'method\n'
+                 'attributes on bound methods is disallowed.  Attempting to '
+                 'set an\n'
+                 'attribute on a method results in an "AttributeError" being '
+                 'raised.  In\n'
+                 'order to set a method attribute, you need to explicitly set '
+                 'it on the\n'
+                 'underlying function object:\n'
+                 '\n'
+                 '   >>> class C:\n'
+                 '   ...     def method(self):\n'
+                 '   ...         pass\n'
+                 '   ...\n'
+                 '   >>> c = C()\n'
+                 "   >>> c.method.whoami = 'my name is method'  # can't set on "
+                 'the method\n'
+                 '   Traceback (most recent call last):\n'
+                 '     File "<stdin>", line 1, in <module>\n'
+                 "   AttributeError: 'method' object has no attribute "
+                 "'whoami'\n"
+                 "   >>> c.method.__func__.whoami = 'my name is method'\n"
+                 '   >>> c.method.whoami\n'
+                 "   'my name is method'\n"
+                 '\n'
+                 'See The standard type hierarchy for more information.\n',
+ 'typesmodules': 'Modules\n'
+                 '*******\n'
+                 '\n'
+                 'The only special operation on a module is attribute access: '
+                 '"m.name",\n'
+                 'where *m* is a module and *name* accesses a name defined in '
+                 '*m*’s\n'
+                 'symbol table. Module attributes can be assigned to.  (Note '
+                 'that the\n'
+                 '"import" statement is not, strictly speaking, an operation '
+                 'on a module\n'
+                 'object; "import foo" does not require a module object named '
+                 '*foo* to\n'
+                 'exist, rather it requires an (external) *definition* for a '
+                 'module\n'
+                 'named *foo* somewhere.)\n'
+                 '\n'
+                 'A special attribute of every module is "__dict__". This is '
+                 'the\n'
+                 'dictionary containing the module’s symbol table. Modifying '
+                 'this\n'
+                 'dictionary will actually change the module’s symbol table, '
+                 'but direct\n'
+                 'assignment to the "__dict__" attribute is not possible (you '
+                 'can write\n'
+                 '"m.__dict__[\'a\'] = 1", which defines "m.a" to be "1", but '
+                 'you can’t\n'
+                 'write "m.__dict__ = {}").  Modifying "__dict__" directly is '
+                 'not\n'
+                 'recommended.\n'
+                 '\n'
+                 'Modules built into the interpreter are written like this: '
+                 '"<module\n'
+                 '\'sys\' (built-in)>".  If loaded from a file, they are '
+                 'written as\n'
+                 '"<module \'os\' from '
+                 '\'/usr/local/lib/pythonX.Y/os.pyc\'>".\n',
+ 'typesseq': 'Sequence Types — "list", "tuple", "range"\n'
+             '*****************************************\n'
+             '\n'
+             'There are three basic sequence types: lists, tuples, and range\n'
+             'objects. Additional sequence types tailored for processing of '
+             'binary\n'
+             'data and text strings are described in dedicated sections.\n'
+             '\n'
+             '\n'
+             'Common Sequence Operations\n'
+             '==========================\n'
+             '\n'
+             'The operations in the following table are supported by most '
+             'sequence\n'
+             'types, both mutable and immutable. The '
+             '"collections.abc.Sequence" ABC\n'
+             'is provided to make it easier to correctly implement these '
+             'operations\n'
+             'on custom sequence types.\n'
+             '\n'
+             'This table lists the sequence operations sorted in ascending '
+             'priority.\n'
+             'In the table, *s* and *t* are sequences of the same type, *n*, '
+             '*i*,\n'
+             '*j* and *k* are integers and *x* is an arbitrary object that '
+             'meets any\n'
+             'type and value restrictions imposed by *s*.\n'
+             '\n'
+             'The "in" and "not in" operations have the same priorities as '
+             'the\n'
+             'comparison operations. The "+" (concatenation) and "*" '
+             '(repetition)\n'
+             'operations have the same priority as the corresponding numeric\n'
+             'operations. [3]\n'
+             '\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| Operation                  | Result                           '
+             '| Notes      |\n'
+             '+============================+==================================+============+\n'
+             '| "x in s"                   | "True" if an item of *s* is      '
+             '| (1)        |\n'
+             '|                            | equal to *x*, else "False"       '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "x not in s"               | "False" if an item of *s* is     '
+             '| (1)        |\n'
+             '|                            | equal to *x*, else "True"        '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s + t"                    | the concatenation of *s* and *t* '
+             '| (6)(7)     |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s * n" or "n * s"         | equivalent to adding *s* to      '
+             '| (2)(7)     |\n'
+             '|                            | itself *n* times                 '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s[i]"                     | *i*th item of *s*, origin 0      '
+             '| (3)        |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s[i:j]"                   | slice of *s* from *i* to *j*     '
+             '| (3)(4)     |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s[i:j:k]"                 | slice of *s* from *i* to *j*     '
+             '| (3)(5)     |\n'
+             '|                            | with step *k*                    '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "len(s)"                   | length of *s*                    '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "min(s)"                   | smallest item of *s*             '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "max(s)"                   | largest item of *s*              '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s.index(x[, i[, j]])"     | index of the first occurrence of '
+             '| (8)        |\n'
+             '|                            | *x* in *s* (at or after index    '
+             '|            |\n'
+             '|                            | *i* and before index *j*)        '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '| "s.count(x)"               | total number of occurrences of   '
+             '|            |\n'
+             '|                            | *x* in *s*                       '
+             '|            |\n'
+             '+----------------------------+----------------------------------+------------+\n'
+             '\n'
+             'Sequences of the same type also support comparisons.  In '
+             'particular,\n'
+             'tuples and lists are compared lexicographically by comparing\n'
+             'corresponding elements. This means that to compare equal, every\n'
+             'element must compare equal and the two sequences must be of the '
+             'same\n'
+             'type and have the same length.  (For full details see '
+             'Comparisons in\n'
+             'the language reference.)\n'
+             '\n'
+             'Notes:\n'
+             '\n'
+             '1. While the "in" and "not in" operations are used only for '
+             'simple\n'
+             '   containment testing in the general case, some specialised '
+             'sequences\n'
+             '   (such as "str", "bytes" and "bytearray") also use them for\n'
+             '   subsequence testing:\n'
+             '\n'
+             '      >>> "gg" in "eggs"\n'
+             '      True\n'
+             '\n'
+             '2. Values of *n* less than "0" are treated as "0" (which yields '
+             'an\n'
+             '   empty sequence of the same type as *s*).  Note that items in '
+             'the\n'
+             '   sequence *s* are not copied; they are referenced multiple '
+             'times.\n'
+             '   This often haunts new Python programmers; consider:\n'
+             '\n'
+             '      >>> lists = [[]] * 3\n'
+             '      >>> lists\n'
+             '      [[], [], []]\n'
+             '      >>> lists[0].append(3)\n'
+             '      >>> lists\n'
+             '      [[3], [3], [3]]\n'
+             '\n'
+             '   What has happened is that "[[]]" is a one-element list '
+             'containing\n'
+             '   an empty list, so all three elements of "[[]] * 3" are '
+             'references\n'
+             '   to this single empty list.  Modifying any of the elements of\n'
+             '   "lists" modifies this single list. You can create a list of\n'
+             '   different lists this way:\n'
+             '\n'
+             '      >>> lists = [[] for i in range(3)]\n'
+             '      >>> lists[0].append(3)\n'
+             '      >>> lists[1].append(5)\n'
+             '      >>> lists[2].append(7)\n'
+             '      >>> lists\n'
+             '      [[3], [5], [7]]\n'
+             '\n'
+             '   Further explanation is available in the FAQ entry How do I '
+             'create a\n'
+             '   multidimensional list?.\n'
+             '\n'
+             '3. If *i* or *j* is negative, the index is relative to the end '
+             'of\n'
+             '   sequence *s*: "len(s) + i" or "len(s) + j" is substituted.  '
+             'But\n'
+             '   note that "-0" is still "0".\n'
+             '\n'
+             '4. The slice of *s* from *i* to *j* is defined as the sequence '
+             'of\n'
+             '   items with index *k* such that "i <= k < j".  If *i* or *j* '
+             'is\n'
+             '   greater than "len(s)", use "len(s)".  If *i* is omitted or '
+             '"None",\n'
+             '   use "0".  If *j* is omitted or "None", use "len(s)".  If *i* '
+             'is\n'
+             '   greater than or equal to *j*, the slice is empty.\n'
+             '\n'
+             '5. The slice of *s* from *i* to *j* with step *k* is defined as '
+             'the\n'
+             '   sequence of items with index  "x = i + n*k" such that "0 <= n '
+             '<\n'
+             '   (j-i)/k".  In other words, the indices are "i", "i+k", '
+             '"i+2*k",\n'
+             '   "i+3*k" and so on, stopping when *j* is reached (but never\n'
+             '   including *j*).  When *k* is positive, *i* and *j* are '
+             'reduced to\n'
+             '   "len(s)" if they are greater. When *k* is negative, *i* and '
+             '*j* are\n'
+             '   reduced to "len(s) - 1" if they are greater.  If *i* or *j* '
+             'are\n'
+             '   omitted or "None", they become “end” values (which end '
+             'depends on\n'
+             '   the sign of *k*).  Note, *k* cannot be zero. If *k* is '
+             '"None", it\n'
+             '   is treated like "1".\n'
+             '\n'
+             '6. Concatenating immutable sequences always results in a new\n'
+             '   object. This means that building up a sequence by repeated\n'
+             '   concatenation will have a quadratic runtime cost in the '
+             'total\n'
+             '   sequence length. To get a linear runtime cost, you must '
+             'switch to\n'
+             '   one of the alternatives below:\n'
+             '\n'
+             '   * if concatenating "str" objects, you can build a list and '
+             'use\n'
+             '     "str.join()" at the end or else write to an "io.StringIO"\n'
+             '     instance and retrieve its value when complete\n'
+             '\n'
+             '   * if concatenating "bytes" objects, you can similarly use\n'
+             '     "bytes.join()" or "io.BytesIO", or you can do in-place\n'
+             '     concatenation with a "bytearray" object.  "bytearray" '
+             'objects are\n'
+             '     mutable and have an efficient overallocation mechanism\n'
+             '\n'
+             '   * if concatenating "tuple" objects, extend a "list" instead\n'
+             '\n'
+             '   * for other types, investigate the relevant class '
+             'documentation\n'
+             '\n'
+             '7. Some sequence types (such as "range") only support item\n'
+             '   sequences that follow specific patterns, and hence don’t '
+             'support\n'
+             '   sequence concatenation or repetition.\n'
+             '\n'
+             '8. "index" raises "ValueError" when *x* is not found in *s*. '
+             'Not\n'
+             '   all implementations support passing the additional arguments '
+             '*i*\n'
+             '   and *j*. These arguments allow efficient searching of '
+             'subsections\n'
+             '   of the sequence. Passing the extra arguments is roughly '
+             'equivalent\n'
+             '   to using "s[i:j].index(x)", only without copying any data and '
+             'with\n'
+             '   the returned index being relative to the start of the '
+             'sequence\n'
+             '   rather than the start of the slice.\n'
+             '\n'
+             '\n'
+             'Immutable Sequence Types\n'
+             '========================\n'
+             '\n'
+             'The only operation that immutable sequence types generally '
+             'implement\n'
+             'that is not also implemented by mutable sequence types is '
+             'support for\n'
+             'the "hash()" built-in.\n'
+             '\n'
+             'This support allows immutable sequences, such as "tuple" '
+             'instances, to\n'
+             'be used as "dict" keys and stored in "set" and "frozenset" '
+             'instances.\n'
+             '\n'
+             'Attempting to hash an immutable sequence that contains '
+             'unhashable\n'
+             'values will result in "TypeError".\n'
+             '\n'
+             '\n'
+             'Mutable Sequence Types\n'
+             '======================\n'
+             '\n'
+             'The operations in the following table are defined on mutable '
+             'sequence\n'
+             'types. The "collections.abc.MutableSequence" ABC is provided to '
+             'make\n'
+             'it easier to correctly implement these operations on custom '
+             'sequence\n'
+             'types.\n'
+             '\n'
+             'In the table *s* is an instance of a mutable sequence type, *t* '
+             'is any\n'
+             'iterable object and *x* is an arbitrary object that meets any '
+             'type and\n'
+             'value restrictions imposed by *s* (for example, "bytearray" '
+             'only\n'
+             'accepts integers that meet the value restriction "0 <= x <= '
+             '255").\n'
+             '\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| Operation                      | '
+             'Result                           | Notes                 |\n'
+             '+================================+==================================+=======================+\n'
+             '| "s[i] = x"                     | item *i* of *s* is replaced '
+             'by   |                       |\n'
+             '|                                | '
+             '*x*                              |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s[i:j] = t"                   | slice of *s* from *i* to *j* '
+             'is  |                       |\n'
+             '|                                | replaced by the contents of '
+             'the  |                       |\n'
+             '|                                | iterable '
+             '*t*                     |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "del s[i:j]"                   | same as "s[i:j] = '
+             '[]"            |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s[i:j:k] = t"                 | the elements of "s[i:j:k]" '
+             'are   | (1)                   |\n'
+             '|                                | replaced by those of '
+             '*t*         |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "del s[i:j:k]"                 | removes the elements '
+             'of          |                       |\n'
+             '|                                | "s[i:j:k]" from the '
+             'list         |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.append(x)"                  | appends *x* to the end of '
+             'the    |                       |\n'
+             '|                                | sequence (same '
+             'as                |                       |\n'
+             '|                                | "s[len(s):len(s)] = '
+             '[x]")        |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.clear()"                    | removes all items from *s* '
+             '(same | (5)                   |\n'
+             '|                                | as "del '
+             's[:]")                   |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.copy()"                     | creates a shallow copy of '
+             '*s*    | (5)                   |\n'
+             '|                                | (same as '
+             '"s[:]")                 |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.extend(t)" or "s += t"      | extends *s* with the contents '
+             'of |                       |\n'
+             '|                                | *t* (for the most part the '
+             'same  |                       |\n'
+             '|                                | as "s[len(s):len(s)] = '
+             't")       |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s *= n"                       | updates *s* with its '
+             'contents    | (6)                   |\n'
+             '|                                | repeated *n* '
+             'times               |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.insert(i, x)"               | inserts *x* into *s* at '
+             'the      |                       |\n'
+             '|                                | index given by *i* (same '
+             'as      |                       |\n'
+             '|                                | "s[i:i] = '
+             '[x]")                  |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.pop([i])"                   | retrieves the item at *i* '
+             'and    | (2)                   |\n'
+             '|                                | also removes it from '
+             '*s*         |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.remove(x)"                  | remove the first item from '
+             '*s*   | (3)                   |\n'
+             '|                                | where "s[i] == '
+             'x"                |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '| "s.reverse()"                  | reverses the items of *s* '
+             'in     | (4)                   |\n'
+             '|                                | '
+             'place                            |                       |\n'
+             '+--------------------------------+----------------------------------+-----------------------+\n'
+             '\n'
+             'Notes:\n'
+             '\n'
+             '1. *t* must have the same length as the slice it is replacing.\n'
+             '\n'
+             '2. The optional argument *i* defaults to "-1", so that by '
+             'default\n'
+             '   the last item is removed and returned.\n'
+             '\n'
+             '3. "remove" raises "ValueError" when *x* is not found in *s*.\n'
+             '\n'
+             '4. The "reverse()" method modifies the sequence in place for\n'
+             '   economy of space when reversing a large sequence.  To remind '
+             'users\n'
+             '   that it operates by side effect, it does not return the '
+             'reversed\n'
+             '   sequence.\n'
+             '\n'
+             '5. "clear()" and "copy()" are included for consistency with the\n'
+             '   interfaces of mutable containers that don’t support slicing\n'
+             '   operations (such as "dict" and "set")\n'
+             '\n'
+             '   New in version 3.3: "clear()" and "copy()" methods.\n'
+             '\n'
+             '6. The value *n* is an integer, or an object implementing\n'
+             '   "__index__()".  Zero and negative values of *n* clear the '
+             'sequence.\n'
+             '   Items in the sequence are not copied; they are referenced '
+             'multiple\n'
+             '   times, as explained for "s * n" under Common Sequence '
+             'Operations.\n'
+             '\n'
+             '\n'
+             'Lists\n'
+             '=====\n'
+             '\n'
+             'Lists are mutable sequences, typically used to store collections '
+             'of\n'
+             'homogeneous items (where the precise degree of similarity will '
+             'vary by\n'
+             'application).\n'
+             '\n'
+             'class list([iterable])\n'
+             '\n'
+             '   Lists may be constructed in several ways:\n'
+             '\n'
+             '   * Using a pair of square brackets to denote the empty list: '
+             '"[]"\n'
+             '\n'
+             '   * Using square brackets, separating items with commas: '
+             '"[a]",\n'
+             '     "[a, b, c]"\n'
+             '\n'
+             '   * Using a list comprehension: "[x for x in iterable]"\n'
+             '\n'
+             '   * Using the type constructor: "list()" or "list(iterable)"\n'
+             '\n'
+             '   The constructor builds a list whose items are the same and in '
+             'the\n'
+             '   same order as *iterable*’s items.  *iterable* may be either '
+             'a\n'
+             '   sequence, a container that supports iteration, or an '
+             'iterator\n'
+             '   object.  If *iterable* is already a list, a copy is made and\n'
+             '   returned, similar to "iterable[:]". For example, '
+             '"list(\'abc\')"\n'
+             '   returns "[\'a\', \'b\', \'c\']" and "list( (1, 2, 3) )" '
+             'returns "[1, 2,\n'
+             '   3]". If no argument is given, the constructor creates a new '
+             'empty\n'
+             '   list, "[]".\n'
+             '\n'
+             '   Many other operations also produce lists, including the '
+             '"sorted()"\n'
+             '   built-in.\n'
+             '\n'
+             '   Lists implement all of the common and mutable sequence '
+             'operations.\n'
+             '   Lists also provide the following additional method:\n'
+             '\n'
+             '   sort(*, key=None, reverse=False)\n'
+             '\n'
+             '      This method sorts the list in place, using only "<" '
+             'comparisons\n'
+             '      between items. Exceptions are not suppressed - if any '
+             'comparison\n'
+             '      operations fail, the entire sort operation will fail (and '
+             'the\n'
+             '      list will likely be left in a partially modified state).\n'
+             '\n'
+             '      "sort()" accepts two arguments that can only be passed by\n'
+             '      keyword (keyword-only arguments):\n'
+             '\n'
+             '      *key* specifies a function of one argument that is used '
+             'to\n'
+             '      extract a comparison key from each list element (for '
+             'example,\n'
+             '      "key=str.lower"). The key corresponding to each item in '
+             'the list\n'
+             '      is calculated once and then used for the entire sorting '
+             'process.\n'
+             '      The default value of "None" means that list items are '
+             'sorted\n'
+             '      directly without calculating a separate key value.\n'
+             '\n'
+             '      The "functools.cmp_to_key()" utility is available to '
+             'convert a\n'
+             '      2.x style *cmp* function to a *key* function.\n'
+             '\n'
+             '      *reverse* is a boolean value.  If set to "True", then the '
+             'list\n'
+             '      elements are sorted as if each comparison were reversed.\n'
+             '\n'
+             '      This method modifies the sequence in place for economy of '
+             'space\n'
+             '      when sorting a large sequence.  To remind users that it '
+             'operates\n'
+             '      by side effect, it does not return the sorted sequence '
+             '(use\n'
+             '      "sorted()" to explicitly request a new sorted list '
+             'instance).\n'
+             '\n'
+             '      The "sort()" method is guaranteed to be stable.  A sort '
+             'is\n'
+             '      stable if it guarantees not to change the relative order '
+             'of\n'
+             '      elements that compare equal — this is helpful for sorting '
+             'in\n'
+             '      multiple passes (for example, sort by department, then by '
+             'salary\n'
+             '      grade).\n'
+             '\n'
+             '      **CPython implementation detail:** While a list is being '
+             'sorted,\n'
+             '      the effect of attempting to mutate, or even inspect, the '
+             'list is\n'
+             '      undefined.  The C implementation of Python makes the list '
+             'appear\n'
+             '      empty for the duration, and raises "ValueError" if it can '
+             'detect\n'
+             '      that the list has been mutated during a sort.\n'
+             '\n'
+             '\n'
+             'Tuples\n'
+             '======\n'
+             '\n'
+             'Tuples are immutable sequences, typically used to store '
+             'collections of\n'
+             'heterogeneous data (such as the 2-tuples produced by the '
+             '"enumerate()"\n'
+             'built-in). Tuples are also used for cases where an immutable '
+             'sequence\n'
+             'of homogeneous data is needed (such as allowing storage in a '
+             '"set" or\n'
+             '"dict" instance).\n'
+             '\n'
+             'class tuple([iterable])\n'
+             '\n'
+             '   Tuples may be constructed in a number of ways:\n'
+             '\n'
+             '   * Using a pair of parentheses to denote the empty tuple: '
+             '"()"\n'
+             '\n'
+             '   * Using a trailing comma for a singleton tuple: "a," or '
+             '"(a,)"\n'
+             '\n'
+             '   * Separating items with commas: "a, b, c" or "(a, b, c)"\n'
+             '\n'
+             '   * Using the "tuple()" built-in: "tuple()" or '
+             '"tuple(iterable)"\n'
+             '\n'
+             '   The constructor builds a tuple whose items are the same and '
+             'in the\n'
+             '   same order as *iterable*’s items.  *iterable* may be either '
+             'a\n'
+             '   sequence, a container that supports iteration, or an '
+             'iterator\n'
+             '   object.  If *iterable* is already a tuple, it is returned\n'
+             '   unchanged. For example, "tuple(\'abc\')" returns "(\'a\', '
+             '\'b\', \'c\')"\n'
+             '   and "tuple( [1, 2, 3] )" returns "(1, 2, 3)". If no argument '
+             'is\n'
+             '   given, the constructor creates a new empty tuple, "()".\n'
+             '\n'
+             '   Note that it is actually the comma which makes a tuple, not '
+             'the\n'
+             '   parentheses. The parentheses are optional, except in the '
+             'empty\n'
+             '   tuple case, or when they are needed to avoid syntactic '
+             'ambiguity.\n'
+             '   For example, "f(a, b, c)" is a function call with three '
+             'arguments,\n'
+             '   while "f((a, b, c))" is a function call with a 3-tuple as the '
+             'sole\n'
+             '   argument.\n'
+             '\n'
+             '   Tuples implement all of the common sequence operations.\n'
+             '\n'
+             'For heterogeneous collections of data where access by name is '
+             'clearer\n'
+             'than access by index, "collections.namedtuple()" may be a more\n'
+             'appropriate choice than a simple tuple object.\n'
+             '\n'
+             '\n'
+             'Ranges\n'
+             '======\n'
+             '\n'
+             'The "range" type represents an immutable sequence of numbers and '
+             'is\n'
+             'commonly used for looping a specific number of times in "for" '
+             'loops.\n'
+             '\n'
+             'class range(stop)\n'
+             'class range(start, stop[, step])\n'
+             '\n'
+             '   The arguments to the range constructor must be integers '
+             '(either\n'
+             '   built-in "int" or any object that implements the "__index__"\n'
+             '   special method).  If the *step* argument is omitted, it '
+             'defaults to\n'
+             '   "1". If the *start* argument is omitted, it defaults to "0". '
+             'If\n'
+             '   *step* is zero, "ValueError" is raised.\n'
+             '\n'
+             '   For a positive *step*, the contents of a range "r" are '
+             'determined\n'
+             '   by the formula "r[i] = start + step*i" where "i >= 0" and '
+             '"r[i] <\n'
+             '   stop".\n'
+             '\n'
+             '   For a negative *step*, the contents of the range are still\n'
+             '   determined by the formula "r[i] = start + step*i", but the\n'
+             '   constraints are "i >= 0" and "r[i] > stop".\n'
+             '\n'
+             '   A range object will be empty if "r[0]" does not meet the '
+             'value\n'
+             '   constraint. Ranges do support negative indices, but these '
+             'are\n'
+             '   interpreted as indexing from the end of the sequence '
+             'determined by\n'
+             '   the positive indices.\n'
+             '\n'
+             '   Ranges containing absolute values larger than "sys.maxsize" '
+             'are\n'
+             '   permitted but some features (such as "len()") may raise\n'
+             '   "OverflowError".\n'
+             '\n'
+             '   Range examples:\n'
+             '\n'
+             '      >>> list(range(10))\n'
+             '      [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n'
+             '      >>> list(range(1, 11))\n'
+             '      [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]\n'
+             '      >>> list(range(0, 30, 5))\n'
+             '      [0, 5, 10, 15, 20, 25]\n'
+             '      >>> list(range(0, 10, 3))\n'
+             '      [0, 3, 6, 9]\n'
+             '      >>> list(range(0, -10, -1))\n'
+             '      [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]\n'
+             '      >>> list(range(0))\n'
+             '      []\n'
+             '      >>> list(range(1, 0))\n'
+             '      []\n'
+             '\n'
+             '   Ranges implement all of the common sequence operations '
+             'except\n'
+             '   concatenation and repetition (due to the fact that range '
+             'objects\n'
+             '   can only represent sequences that follow a strict pattern '
+             'and\n'
+             '   repetition and concatenation will usually violate that '
+             'pattern).\n'
+             '\n'
+             '   start\n'
+             '\n'
+             '      The value of the *start* parameter (or "0" if the '
+             'parameter was\n'
+             '      not supplied)\n'
+             '\n'
+             '   stop\n'
+             '\n'
+             '      The value of the *stop* parameter\n'
+             '\n'
+             '   step\n'
+             '\n'
+             '      The value of the *step* parameter (or "1" if the parameter '
+             'was\n'
+             '      not supplied)\n'
+             '\n'
+             'The advantage of the "range" type over a regular "list" or '
+             '"tuple" is\n'
+             'that a "range" object will always take the same (small) amount '
+             'of\n'
+             'memory, no matter the size of the range it represents (as it '
+             'only\n'
+             'stores the "start", "stop" and "step" values, calculating '
+             'individual\n'
+             'items and subranges as needed).\n'
+             '\n'
+             'Range objects implement the "collections.abc.Sequence" ABC, and\n'
+             'provide features such as containment tests, element index '
+             'lookup,\n'
+             'slicing and support for negative indices (see Sequence Types — '
+             'list,\n'
+             'tuple, range):\n'
+             '\n'
+             '>>> r = range(0, 20, 2)\n'
+             '>>> r\n'
+             'range(0, 20, 2)\n'
+             '>>> 11 in r\n'
+             'False\n'
+             '>>> 10 in r\n'
+             'True\n'
+             '>>> r.index(10)\n'
+             '5\n'
+             '>>> r[5]\n'
+             '10\n'
+             '>>> r[:5]\n'
+             'range(0, 10, 2)\n'
+             '>>> r[-1]\n'
+             '18\n'
+             '\n'
+             'Testing range objects for equality with "==" and "!=" compares '
+             'them as\n'
+             'sequences.  That is, two range objects are considered equal if '
+             'they\n'
+             'represent the same sequence of values.  (Note that two range '
+             'objects\n'
+             'that compare equal might have different "start", "stop" and '
+             '"step"\n'
+             'attributes, for example "range(0) == range(2, 1, 3)" or '
+             '"range(0, 3,\n'
+             '2) == range(0, 4, 2)".)\n'
+             '\n'
+             'Changed in version 3.2: Implement the Sequence ABC. Support '
+             'slicing\n'
+             'and negative indices. Test "int" objects for membership in '
+             'constant\n'
+             'time instead of iterating through all items.\n'
+             '\n'
+             'Changed in version 3.3: Define ‘==’ and ‘!=’ to compare range '
+             'objects\n'
+             'based on the sequence of values they define (instead of '
+             'comparing\n'
+             'based on object identity).\n'
+             '\n'
+             'New in version 3.3: The "start", "stop" and "step" attributes.\n'
+             '\n'
+             'See also:\n'
+             '\n'
+             '  * The linspace recipe shows how to implement a lazy version '
+             'of\n'
+             '    range suitable for floating point applications.\n',
+ 'typesseq-mutable': 'Mutable Sequence Types\n'
+                     '**********************\n'
+                     '\n'
+                     'The operations in the following table are defined on '
+                     'mutable sequence\n'
+                     'types. The "collections.abc.MutableSequence" ABC is '
+                     'provided to make\n'
+                     'it easier to correctly implement these operations on '
+                     'custom sequence\n'
+                     'types.\n'
+                     '\n'
+                     'In the table *s* is an instance of a mutable sequence '
+                     'type, *t* is any\n'
+                     'iterable object and *x* is an arbitrary object that '
+                     'meets any type and\n'
+                     'value restrictions imposed by *s* (for example, '
+                     '"bytearray" only\n'
+                     'accepts integers that meet the value restriction "0 <= x '
+                     '<= 255").\n'
+                     '\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| Operation                      | '
+                     'Result                           | Notes                 '
+                     '|\n'
+                     '+================================+==================================+=======================+\n'
+                     '| "s[i] = x"                     | item *i* of *s* is '
+                     'replaced by   |                       |\n'
+                     '|                                | '
+                     '*x*                              |                       '
+                     '|\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s[i:j] = t"                   | slice of *s* from *i* '
+                     'to *j* is  |                       |\n'
+                     '|                                | replaced by the '
+                     'contents of the  |                       |\n'
+                     '|                                | iterable '
+                     '*t*                     |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "del s[i:j]"                   | same as "s[i:j] = '
+                     '[]"            |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s[i:j:k] = t"                 | the elements of '
+                     '"s[i:j:k]" are   | (1)                   |\n'
+                     '|                                | replaced by those of '
+                     '*t*         |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "del s[i:j:k]"                 | removes the elements '
+                     'of          |                       |\n'
+                     '|                                | "s[i:j:k]" from the '
+                     'list         |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.append(x)"                  | appends *x* to the '
+                     'end of the    |                       |\n'
+                     '|                                | sequence (same '
+                     'as                |                       |\n'
+                     '|                                | "s[len(s):len(s)] = '
+                     '[x]")        |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.clear()"                    | removes all items '
+                     'from *s* (same | (5)                   |\n'
+                     '|                                | as "del '
+                     's[:]")                   |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.copy()"                     | creates a shallow '
+                     'copy of *s*    | (5)                   |\n'
+                     '|                                | (same as '
+                     '"s[:]")                 |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.extend(t)" or "s += t"      | extends *s* with the '
+                     'contents of |                       |\n'
+                     '|                                | *t* (for the most '
+                     'part the same  |                       |\n'
+                     '|                                | as "s[len(s):len(s)] '
+                     '= t")       |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s *= n"                       | updates *s* with its '
+                     'contents    | (6)                   |\n'
+                     '|                                | repeated *n* '
+                     'times               |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.insert(i, x)"               | inserts *x* into *s* '
+                     'at the      |                       |\n'
+                     '|                                | index given by *i* '
+                     '(same as      |                       |\n'
+                     '|                                | "s[i:i] = '
+                     '[x]")                  |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.pop([i])"                   | retrieves the item at '
+                     '*i* and    | (2)                   |\n'
+                     '|                                | also removes it from '
+                     '*s*         |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.remove(x)"                  | remove the first item '
+                     'from *s*   | (3)                   |\n'
+                     '|                                | where "s[i] == '
+                     'x"                |                       |\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '| "s.reverse()"                  | reverses the items of '
+                     '*s* in     | (4)                   |\n'
+                     '|                                | '
+                     'place                            |                       '
+                     '|\n'
+                     '+--------------------------------+----------------------------------+-----------------------+\n'
+                     '\n'
+                     'Notes:\n'
+                     '\n'
+                     '1. *t* must have the same length as the slice it is '
+                     'replacing.\n'
+                     '\n'
+                     '2. The optional argument *i* defaults to "-1", so that '
+                     'by default\n'
+                     '   the last item is removed and returned.\n'
+                     '\n'
+                     '3. "remove" raises "ValueError" when *x* is not found in '
+                     '*s*.\n'
+                     '\n'
+                     '4. The "reverse()" method modifies the sequence in place '
+                     'for\n'
+                     '   economy of space when reversing a large sequence.  To '
+                     'remind users\n'
+                     '   that it operates by side effect, it does not return '
+                     'the reversed\n'
+                     '   sequence.\n'
+                     '\n'
+                     '5. "clear()" and "copy()" are included for consistency '
+                     'with the\n'
+                     '   interfaces of mutable containers that don’t support '
+                     'slicing\n'
+                     '   operations (such as "dict" and "set")\n'
+                     '\n'
+                     '   New in version 3.3: "clear()" and "copy()" methods.\n'
+                     '\n'
+                     '6. The value *n* is an integer, or an object '
+                     'implementing\n'
+                     '   "__index__()".  Zero and negative values of *n* clear '
+                     'the sequence.\n'
+                     '   Items in the sequence are not copied; they are '
+                     'referenced multiple\n'
+                     '   times, as explained for "s * n" under Common Sequence '
+                     'Operations.\n',
+ 'unary': 'Unary arithmetic and bitwise operations\n'
+          '***************************************\n'
+          '\n'
+          'All unary arithmetic and bitwise operations have the same '
+          'priority:\n'
+          '\n'
+          '   u_expr ::= power | "-" u_expr | "+" u_expr | "~" u_expr\n'
+          '\n'
+          'The unary "-" (minus) operator yields the negation of its numeric\n'
+          'argument.\n'
+          '\n'
+          'The unary "+" (plus) operator yields its numeric argument '
+          'unchanged.\n'
+          '\n'
+          'The unary "~" (invert) operator yields the bitwise inversion of '
+          'its\n'
+          'integer argument.  The bitwise inversion of "x" is defined as\n'
+          '"-(x+1)".  It only applies to integral numbers.\n'
+          '\n'
+          'In all three cases, if the argument does not have the proper type, '
+          'a\n'
+          '"TypeError" exception is raised.\n',
+ 'while': 'The "while" statement\n'
+          '*********************\n'
+          '\n'
+          'The "while" statement is used for repeated execution as long as an\n'
+          'expression is true:\n'
+          '\n'
+          '   while_stmt ::= "while" expression ":" suite\n'
+          '                  ["else" ":" suite]\n'
+          '\n'
+          'This repeatedly tests the expression and, if it is true, executes '
+          'the\n'
+          'first suite; if the expression is false (which may be the first '
+          'time\n'
+          'it is tested) the suite of the "else" clause, if present, is '
+          'executed\n'
+          'and the loop terminates.\n'
+          '\n'
+          'A "break" statement executed in the first suite terminates the '
+          'loop\n'
+          'without executing the "else" clause’s suite.  A "continue" '
+          'statement\n'
+          'executed in the first suite skips the rest of the suite and goes '
+          'back\n'
+          'to testing the expression.\n',
+ 'with': 'The "with" statement\n'
+         '********************\n'
+         '\n'
+         'The "with" statement is used to wrap the execution of a block with\n'
+         'methods defined by a context manager (see section With Statement\n'
+         'Context Managers). This allows common "try"…"except"…"finally" '
+         'usage\n'
+         'patterns to be encapsulated for convenient reuse.\n'
+         '\n'
+         '   with_stmt ::= "with" with_item ("," with_item)* ":" suite\n'
+         '   with_item ::= expression ["as" target]\n'
+         '\n'
+         'The execution of the "with" statement with one “item” proceeds as\n'
+         'follows:\n'
+         '\n'
+         '1. The context expression (the expression given in the "with_item")\n'
+         '   is evaluated to obtain a context manager.\n'
+         '\n'
+         '2. The context manager’s "__exit__()" is loaded for later use.\n'
+         '\n'
+         '3. The context manager’s "__enter__()" method is invoked.\n'
+         '\n'
+         '4. If a target was included in the "with" statement, the return\n'
+         '   value from "__enter__()" is assigned to it.\n'
+         '\n'
+         '   Note: The "with" statement guarantees that if the "__enter__()"\n'
+         '     method returns without an error, then "__exit__()" will always '
+         'be\n'
+         '     called. Thus, if an error occurs during the assignment to the\n'
+         '     target list, it will be treated the same as an error occurring\n'
+         '     within the suite would be. See step 6 below.\n'
+         '\n'
+         '5. The suite is executed.\n'
+         '\n'
+         '6. The context manager’s "__exit__()" method is invoked.  If an\n'
+         '   exception caused the suite to be exited, its type, value, and\n'
+         '   traceback are passed as arguments to "__exit__()". Otherwise, '
+         'three\n'
+         '   "None" arguments are supplied.\n'
+         '\n'
+         '   If the suite was exited due to an exception, and the return '
+         'value\n'
+         '   from the "__exit__()" method was false, the exception is '
+         'reraised.\n'
+         '   If the return value was true, the exception is suppressed, and\n'
+         '   execution continues with the statement following the "with"\n'
+         '   statement.\n'
+         '\n'
+         '   If the suite was exited for any reason other than an exception, '
+         'the\n'
+         '   return value from "__exit__()" is ignored, and execution '
+         'proceeds\n'
+         '   at the normal location for the kind of exit that was taken.\n'
+         '\n'
+         'With more than one item, the context managers are processed as if\n'
+         'multiple "with" statements were nested:\n'
+         '\n'
+         '   with A() as a, B() as b:\n'
+         '       suite\n'
+         '\n'
+         'is equivalent to\n'
+         '\n'
+         '   with A() as a:\n'
+         '       with B() as b:\n'
+         '           suite\n'
+         '\n'
+         'Changed in version 3.1: Support for multiple context expressions.\n'
+         '\n'
+         'See also:\n'
+         '\n'
+         '  **PEP 343** - The “with” statement\n'
+         '     The specification, background, and examples for the Python '
+         '"with"\n'
+         '     statement.\n',
+ 'yield': 'The "yield" statement\n'
+          '*********************\n'
+          '\n'
+          '   yield_stmt ::= yield_expression\n'
+          '\n'
+          'A "yield" statement is semantically equivalent to a yield '
+          'expression.\n'
+          'The yield statement can be used to omit the parentheses that would\n'
+          'otherwise be required in the equivalent yield expression '
+          'statement.\n'
+          'For example, the yield statements\n'
+          '\n'
+          '   yield <expr>\n'
+          '   yield from <expr>\n'
+          '\n'
+          'are equivalent to the yield expression statements\n'
+          '\n'
+          '   (yield <expr>)\n'
+          '   (yield from <expr>)\n'
+          '\n'
+          'Yield expressions and statements are only used when defining a\n'
+          '*generator* function, and are only used in the body of the '
+          'generator\n'
+          'function.  Using yield in a function definition is sufficient to '
+          'cause\n'
+          'that definition to create a generator function instead of a normal\n'
+          'function.\n'
+          '\n'
+          'For full details of "yield" semantics, refer to the Yield '
+          'expressions\n'
+          'section.\n'}
diff --git a/Lib/quopri.py b/Lib/quopri.py
new file mode 100755
index 000000000..de1e19acd
--- /dev/null
+++ b/Lib/quopri.py
@@ -0,0 +1,242 @@
+#! /usr/bin/python3.6
+
+"""Conversions to/from quoted-printable transport encoding as per RFC 1521."""
+
+# (Dec 1991 version).
+
+__all__ = ["encode", "decode", "encodestring", "decodestring"]
+
+ESCAPE = b'='
+MAXLINESIZE = 76
+HEX = b'0123456789ABCDEF'
+EMPTYSTRING = b''
+
+try:
+    from binascii import a2b_qp, b2a_qp
+except ImportError:
+    a2b_qp = None
+    b2a_qp = None
+
+
+def needsquoting(c, quotetabs, header):
+    """Decide whether a particular byte ordinal needs to be quoted.
+
+    The 'quotetabs' flag indicates whether embedded tabs and spaces should be
+    quoted.  Note that line-ending tabs and spaces are always encoded, as per
+    RFC 1521.
+    """
+    assert isinstance(c, bytes)
+    if c in b' \t':
+        return quotetabs
+    # if header, we have to escape _ because _ is used to escape space
+    if c == b'_':
+        return header
+    return c == ESCAPE or not (b' ' <= c <= b'~')
+
+def quote(c):
+    """Quote a single character."""
+    assert isinstance(c, bytes) and len(c)==1
+    c = ord(c)
+    return ESCAPE + bytes((HEX[c//16], HEX[c%16]))
+
+
+
+def encode(input, output, quotetabs, header=False):
+    """Read 'input', apply quoted-printable encoding, and write to 'output'.
+
+    'input' and 'output' are binary file objects. The 'quotetabs' flag
+    indicates whether embedded tabs and spaces should be quoted. Note that
+    line-ending tabs and spaces are always encoded, as per RFC 1521.
+    The 'header' flag indicates whether we are encoding spaces as _ as per RFC
+    1522."""
+
+    if b2a_qp is not None:
+        data = input.read()
+        odata = b2a_qp(data, quotetabs=quotetabs, header=header)
+        output.write(odata)
+        return
+
+    def write(s, output=output, lineEnd=b'\n'):
+        # RFC 1521 requires that the line ending in a space or tab must have
+        # that trailing character encoded.
+        if s and s[-1:] in b' \t':
+            output.write(s[:-1] + quote(s[-1:]) + lineEnd)
+        elif s == b'.':
+            output.write(quote(s) + lineEnd)
+        else:
+            output.write(s + lineEnd)
+
+    prevline = None
+    while 1:
+        line = input.readline()
+        if not line:
+            break
+        outline = []
+        # Strip off any readline induced trailing newline
+        stripped = b''
+        if line[-1:] == b'\n':
+            line = line[:-1]
+            stripped = b'\n'
+        # Calculate the un-length-limited encoded line
+        for c in line:
+            c = bytes((c,))
+            if needsquoting(c, quotetabs, header):
+                c = quote(c)
+            if header and c == b' ':
+                outline.append(b'_')
+            else:
+                outline.append(c)
+        # First, write out the previous line
+        if prevline is not None:
+            write(prevline)
+        # Now see if we need any soft line breaks because of RFC-imposed
+        # length limitations.  Then do the thisline->prevline dance.
+        thisline = EMPTYSTRING.join(outline)
+        while len(thisline) > MAXLINESIZE:
+            # Don't forget to include the soft line break `=' sign in the
+            # length calculation!
+            write(thisline[:MAXLINESIZE-1], lineEnd=b'=\n')
+            thisline = thisline[MAXLINESIZE-1:]
+        # Write out the current line
+        prevline = thisline
+    # Write out the last line, without a trailing newline
+    if prevline is not None:
+        write(prevline, lineEnd=stripped)
+
+def encodestring(s, quotetabs=False, header=False):
+    if b2a_qp is not None:
+        return b2a_qp(s, quotetabs=quotetabs, header=header)
+    from io import BytesIO
+    infp = BytesIO(s)
+    outfp = BytesIO()
+    encode(infp, outfp, quotetabs, header)
+    return outfp.getvalue()
+
+
+
+def decode(input, output, header=False):
+    """Read 'input', apply quoted-printable decoding, and write to 'output'.
+    'input' and 'output' are binary file objects.
+    If 'header' is true, decode underscore as space (per RFC 1522)."""
+
+    if a2b_qp is not None:
+        data = input.read()
+        odata = a2b_qp(data, header=header)
+        output.write(odata)
+        return
+
+    new = b''
+    while 1:
+        line = input.readline()
+        if not line: break
+        i, n = 0, len(line)
+        if n > 0 and line[n-1:n] == b'\n':
+            partial = 0; n = n-1
+            # Strip trailing whitespace
+            while n > 0 and line[n-1:n] in b" \t\r":
+                n = n-1
+        else:
+            partial = 1
+        while i < n:
+            c = line[i:i+1]
+            if c == b'_' and header:
+                new = new + b' '; i = i+1
+            elif c != ESCAPE:
+                new = new + c; i = i+1
+            elif i+1 == n and not partial:
+                partial = 1; break
+            elif i+1 < n and line[i+1:i+2] == ESCAPE:
+                new = new + ESCAPE; i = i+2
+            elif i+2 < n and ishex(line[i+1:i+2]) and ishex(line[i+2:i+3]):
+                new = new + bytes((unhex(line[i+1:i+3]),)); i = i+3
+            else: # Bad escape sequence -- leave it in
+                new = new + c; i = i+1
+        if not partial:
+            output.write(new + b'\n')
+            new = b''
+    if new:
+        output.write(new)
+
+def decodestring(s, header=False):
+    if a2b_qp is not None:
+        return a2b_qp(s, header=header)
+    from io import BytesIO
+    infp = BytesIO(s)
+    outfp = BytesIO()
+    decode(infp, outfp, header=header)
+    return outfp.getvalue()
+
+
+
+# Other helper functions
+def ishex(c):
+    """Return true if the byte ordinal 'c' is a hexadecimal digit in ASCII."""
+    assert isinstance(c, bytes)
+    return b'0' <= c <= b'9' or b'a' <= c <= b'f' or b'A' <= c <= b'F'
+
+def unhex(s):
+    """Get the integer value of a hexadecimal number."""
+    bits = 0
+    for c in s:
+        c = bytes((c,))
+        if b'0' <= c <= b'9':
+            i = ord('0')
+        elif b'a' <= c <= b'f':
+            i = ord('a')-10
+        elif b'A' <= c <= b'F':
+            i = ord(b'A')-10
+        else:
+            assert False, "non-hex digit "+repr(c)
+        bits = bits*16 + (ord(c) - i)
+    return bits
+
+
+
+def main():
+    import sys
+    import getopt
+    try:
+        opts, args = getopt.getopt(sys.argv[1:], 'td')
+    except getopt.error as msg:
+        sys.stdout = sys.stderr
+        print(msg)
+        print("usage: quopri [-t | -d] [file] ...")
+        print("-t: quote tabs")
+        print("-d: decode; default encode")
+        sys.exit(2)
+    deco = 0
+    tabs = 0
+    for o, a in opts:
+        if o == '-t': tabs = 1
+        if o == '-d': deco = 1
+    if tabs and deco:
+        sys.stdout = sys.stderr
+        print("-t and -d are mutually exclusive")
+        sys.exit(2)
+    if not args: args = ['-']
+    sts = 0
+    for file in args:
+        if file == '-':
+            fp = sys.stdin.buffer
+        else:
+            try:
+                fp = open(file, "rb")
+            except OSError as msg:
+                sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
+                sts = 1
+                continue
+        try:
+            if deco:
+                decode(fp, sys.stdout.buffer)
+            else:
+                encode(fp, sys.stdout.buffer, tabs)
+        finally:
+            if file != '-':
+                fp.close()
+    if sts:
+        sys.exit(sts)
+
+
+
+if __name__ == '__main__':
+    main()
diff --git a/Lib/sitecustomize.py b/Lib/sitecustomize.py
new file mode 120000
index 000000000..92a663dd3
--- /dev/null
+++ b/Lib/sitecustomize.py
@@ -0,0 +1 @@
+/etc/python3.6/sitecustomize.py
\ No newline at end of file
diff --git a/Lib/wsgiref/__init__.py b/Lib/wsgiref/__init__.py
new file mode 100644
index 000000000..1efbba01a
--- /dev/null
+++ b/Lib/wsgiref/__init__.py
@@ -0,0 +1,23 @@
+"""wsgiref -- a WSGI (PEP 3333) Reference Library
+
+Current Contents:
+
+* util -- Miscellaneous useful functions and wrappers
+
+* headers -- Manage response headers
+
+* handlers -- base classes for server/gateway implementations
+
+* simple_server -- a simple BaseHTTPServer that supports WSGI
+
+* validate -- validation wrapper that sits between an app and a server
+  to detect errors in either
+
+To-Do:
+
+* cgi_gateway -- Run WSGI apps under CGI (pending a deployment standard)
+
+* cgi_wrapper -- Run CGI apps under WSGI
+
+* router -- a simple middleware component that handles URL traversal
+"""
diff --git a/Lib/wsgiref/handlers.py b/Lib/wsgiref/handlers.py
new file mode 100644
index 000000000..f4300b831
--- /dev/null
+++ b/Lib/wsgiref/handlers.py
@@ -0,0 +1,557 @@
+"""Base classes for server/gateway implementations"""
+
+from .util import FileWrapper, guess_scheme, is_hop_by_hop
+from .headers import Headers
+
+import sys, os, time
+
+__all__ = [
+    'BaseHandler', 'SimpleHandler', 'BaseCGIHandler', 'CGIHandler',
+    'IISCGIHandler', 'read_environ'
+]
+
+# Weekday and month names for HTTP date/time formatting; always English!
+_weekdayname = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
+_monthname = [None, # Dummy so we can use 1-based month numbers
+              "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+              "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
+
+def format_date_time(timestamp):
+    year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp)
+    return "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (
+        _weekdayname[wd], day, _monthname[month], year, hh, mm, ss
+    )
+
+_is_request = {
+    'SCRIPT_NAME', 'PATH_INFO', 'QUERY_STRING', 'REQUEST_METHOD', 'AUTH_TYPE',
+    'CONTENT_TYPE', 'CONTENT_LENGTH', 'HTTPS', 'REMOTE_USER', 'REMOTE_IDENT',
+}.__contains__
+
+def _needs_transcode(k):
+    return _is_request(k) or k.startswith('HTTP_') or k.startswith('SSL_') \
+        or (k.startswith('REDIRECT_') and _needs_transcode(k[9:]))
+
+def read_environ():
+    """Read environment, fixing HTTP variables"""
+    enc = sys.getfilesystemencoding()
+    esc = 'surrogateescape'
+    try:
+        ''.encode('utf-8', esc)
+    except LookupError:
+        esc = 'replace'
+    environ = {}
+
+    # Take the basic environment from native-unicode os.environ. Attempt to
+    # fix up the variables that come from the HTTP request to compensate for
+    # the bytes->unicode decoding step that will already have taken place.
+    for k, v in os.environ.items():
+        if _needs_transcode(k):
+
+            # On win32, the os.environ is natively Unicode. Different servers
+            # decode the request bytes using different encodings.
+            if sys.platform == 'win32':
+                software = os.environ.get('SERVER_SOFTWARE', '').lower()
+
+                # On IIS, the HTTP request will be decoded as UTF-8 as long
+                # as the input is a valid UTF-8 sequence. Otherwise it is
+                # decoded using the system code page (mbcs), with no way to
+                # detect this has happened. Because UTF-8 is the more likely
+                # encoding, and mbcs is inherently unreliable (an mbcs string
+                # that happens to be valid UTF-8 will not be decoded as mbcs)
+                # always recreate the original bytes as UTF-8.
+                if software.startswith('microsoft-iis/'):
+                    v = v.encode('utf-8').decode('iso-8859-1')
+
+                # Apache mod_cgi writes bytes-as-unicode (as if ISO-8859-1) direct
+                # to the Unicode environ. No modification needed.
+                elif software.startswith('apache/'):
+                    pass
+
+                # Python 3's http.server.CGIHTTPRequestHandler decodes
+                # using the urllib.unquote default of UTF-8, amongst other
+                # issues.
+                elif (
+                    software.startswith('simplehttp/')
+                    and 'python/3' in software
+                ):
+                    v = v.encode('utf-8').decode('iso-8859-1')
+
+                # For other servers, guess that they have written bytes to
+                # the environ using stdio byte-oriented interfaces, ending up
+                # with the system code page.
+                else:
+                    v = v.encode(enc, 'replace').decode('iso-8859-1')
+
+            # Recover bytes from unicode environ, using surrogate escapes
+            # where available (Python 3.1+).
+            else:
+                v = v.encode(enc, esc).decode('iso-8859-1')
+
+        environ[k] = v
+    return environ
+
+
+class BaseHandler:
+    """Manage the invocation of a WSGI application"""
+
+    # Configuration parameters; can override per-subclass or per-instance
+    wsgi_version = (1,0)
+    wsgi_multithread = True
+    wsgi_multiprocess = True
+    wsgi_run_once = False
+
+    origin_server = True    # We are transmitting direct to client
+    http_version  = "1.0"   # Version that should be used for response
+    server_software = None  # String name of server software, if any
+
+    # os_environ is used to supply configuration from the OS environment:
+    # by default it's a copy of 'os.environ' as of import time, but you can
+    # override this in e.g. your __init__ method.
+    os_environ= read_environ()
+
+    # Collaborator classes
+    wsgi_file_wrapper = FileWrapper     # set to None to disable
+    headers_class = Headers             # must be a Headers-like class
+
+    # Error handling (also per-subclass or per-instance)
+    traceback_limit = None  # Print entire traceback to self.get_stderr()
+    error_status = "500 Internal Server Error"
+    error_headers = [('Content-Type','text/plain')]
+    error_body = b"A server error occurred.  Please contact the administrator."
+
+    # State variables (don't mess with these)
+    status = result = None
+    headers_sent = False
+    headers = None
+    bytes_sent = 0
+
+    def run(self, application):
+        """Invoke the application"""
+        # Note to self: don't move the close()!  Asynchronous servers shouldn't
+        # call close() from finish_response(), so if you close() anywhere but
+        # the double-error branch here, you'll break asynchronous servers by
+        # prematurely closing.  Async servers must return from 'run()' without
+        # closing if there might still be output to iterate over.
+        try:
+            self.setup_environ()
+            self.result = application(self.environ, self.start_response)
+            self.finish_response()
+        except:
+            try:
+                self.handle_error()
+            except:
+                # If we get an error handling an error, just give up already!
+                self.close()
+                raise   # ...and let the actual server figure it out.
+
+
+    def setup_environ(self):
+        """Set up the environment for one request"""
+
+        env = self.environ = self.os_environ.copy()
+        self.add_cgi_vars()
+
+        env['wsgi.input']        = self.get_stdin()
+        env['wsgi.errors']       = self.get_stderr()
+        env['wsgi.version']      = self.wsgi_version
+        env['wsgi.run_once']     = self.wsgi_run_once
+        env['wsgi.url_scheme']   = self.get_scheme()
+        env['wsgi.multithread']  = self.wsgi_multithread
+        env['wsgi.multiprocess'] = self.wsgi_multiprocess
+
+        if self.wsgi_file_wrapper is not None:
+            env['wsgi.file_wrapper'] = self.wsgi_file_wrapper
+
+        if self.origin_server and self.server_software:
+            env.setdefault('SERVER_SOFTWARE',self.server_software)
+
+
+    def finish_response(self):
+        """Send any iterable data, then close self and the iterable
+
+        Subclasses intended for use in asynchronous servers will
+        want to redefine this method, such that it sets up callbacks
+        in the event loop to iterate over the data, and to call
+        'self.close()' once the response is finished.
+        """
+        try:
+            if not self.result_is_file() or not self.sendfile():
+                for data in self.result:
+                    self.write(data)
+                self.finish_content()
+        finally:
+            self.close()
+
+
+    def get_scheme(self):
+        """Return the URL scheme being used"""
+        return guess_scheme(self.environ)
+
+
+    def set_content_length(self):
+        """Compute Content-Length or switch to chunked encoding if possible"""
+        try:
+            blocks = len(self.result)
+        except (TypeError,AttributeError,NotImplementedError):
+            pass
+        else:
+            if blocks==1:
+                self.headers['Content-Length'] = str(self.bytes_sent)
+                return
+        # XXX Try for chunked encoding if origin server and client is 1.1
+
+
+    def cleanup_headers(self):
+        """Make any necessary header changes or defaults
+
+        Subclasses can extend this to add other defaults.
+        """
+        if 'Content-Length' not in self.headers:
+            self.set_content_length()
+
+    def start_response(self, status, headers,exc_info=None):
+        """'start_response()' callable as specified by PEP 3333"""
+
+        if exc_info:
+            try:
+                if self.headers_sent:
+                    # Re-raise original exception if headers sent
+                    raise exc_info[0](exc_info[1]).with_traceback(exc_info[2])
+            finally:
+                exc_info = None        # avoid dangling circular ref
+        elif self.headers is not None:
+            raise AssertionError("Headers already set!")
+
+        self.status = status
+        self.headers = self.headers_class(headers)
+        status = self._convert_string_type(status, "Status")
+        assert len(status)>=4,"Status must be at least 4 characters"
+        assert status[:3].isdigit(), "Status message must begin w/3-digit code"
+        assert status[3]==" ", "Status message must have a space after code"
+
+        if __debug__:
+            for name, val in headers:
+                name = self._convert_string_type(name, "Header name")
+                val = self._convert_string_type(val, "Header value")
+                assert not is_hop_by_hop(name),"Hop-by-hop headers not allowed"
+
+        return self.write
+
+    def _convert_string_type(self, value, title):
+        """Convert/check value type."""
+        if type(value) is str:
+            return value
+        raise AssertionError(
+            "{0} must be of type str (got {1})".format(title, repr(value))
+        )
+
+    def send_preamble(self):
+        """Transmit version/status/date/server, via self._write()"""
+        if self.origin_server:
+            if self.client_is_modern():
+                self._write(('HTTP/%s %s\r\n' % (self.http_version,self.status)).encode('iso-8859-1'))
+                if 'Date' not in self.headers:
+                    self._write(
+                        ('Date: %s\r\n' % format_date_time(time.time())).encode('iso-8859-1')
+                    )
+                if self.server_software and 'Server' not in self.headers:
+                    self._write(('Server: %s\r\n' % self.server_software).encode('iso-8859-1'))
+        else:
+            self._write(('Status: %s\r\n' % self.status).encode('iso-8859-1'))
+
+    def write(self, data):
+        """'write()' callable as specified by PEP 3333"""
+
+        assert type(data) is bytes, \
+            "write() argument must be a bytes instance"
+
+        if not self.status:
+            raise AssertionError("write() before start_response()")
+
+        elif not self.headers_sent:
+            # Before the first output, send the stored headers
+            self.bytes_sent = len(data)    # make sure we know content-length
+            self.send_headers()
+        else:
+            self.bytes_sent += len(data)
+
+        # XXX check Content-Length and truncate if too many bytes written?
+        self._write(data)
+        self._flush()
+
+
+    def sendfile(self):
+        """Platform-specific file transmission
+
+        Override this method in subclasses to support platform-specific
+        file transmission.  It is only called if the application's
+        return iterable ('self.result') is an instance of
+        'self.wsgi_file_wrapper'.
+
+        This method should return a true value if it was able to actually
+        transmit the wrapped file-like object using a platform-specific
+        approach.  It should return a false value if normal iteration
+        should be used instead.  An exception can be raised to indicate
+        that transmission was attempted, but failed.
+
+        NOTE: this method should call 'self.send_headers()' if
+        'self.headers_sent' is false and it is going to attempt direct
+        transmission of the file.
+        """
+        return False   # No platform-specific transmission by default
+
+
+    def finish_content(self):
+        """Ensure headers and content have both been sent"""
+        if not self.headers_sent:
+            # Only zero Content-Length if not set by the application (so
+            # that HEAD requests can be satisfied properly, see #3839)
+            self.headers.setdefault('Content-Length', "0")
+            self.send_headers()
+        else:
+            pass # XXX check if content-length was too short?
+
+    def close(self):
+        """Close the iterable (if needed) and reset all instance vars
+
+        Subclasses may want to also drop the client connection.
+        """
+        try:
+            if hasattr(self.result,'close'):
+                self.result.close()
+        finally:
+            self.result = self.headers = self.status = self.environ = None
+            self.bytes_sent = 0; self.headers_sent = False
+
+
+    def send_headers(self):
+        """Transmit headers to the client, via self._write()"""
+        self.cleanup_headers()
+        self.headers_sent = True
+        if not self.origin_server or self.client_is_modern():
+            self.send_preamble()
+            self._write(bytes(self.headers))
+
+
+    def result_is_file(self):
+        """True if 'self.result' is an instance of 'self.wsgi_file_wrapper'"""
+        wrapper = self.wsgi_file_wrapper
+        return wrapper is not None and isinstance(self.result,wrapper)
+
+
+    def client_is_modern(self):
+        """True if client can accept status and headers"""
+        return self.environ['SERVER_PROTOCOL'].upper() != 'HTTP/0.9'
+
+
+    def log_exception(self,exc_info):
+        """Log the 'exc_info' tuple in the server log
+
+        Subclasses may override to retarget the output or change its format.
+        """
+        try:
+            from traceback import print_exception
+            stderr = self.get_stderr()
+            print_exception(
+                exc_info[0], exc_info[1], exc_info[2],
+                self.traceback_limit, stderr
+            )
+            stderr.flush()
+        finally:
+            exc_info = None
+
+    def handle_error(self):
+        """Log current error, and send error output to client if possible"""
+        self.log_exception(sys.exc_info())
+        if not self.headers_sent:
+            self.result = self.error_output(self.environ, self.start_response)
+            self.finish_response()
+        # XXX else: attempt advanced recovery techniques for HTML or text?
+
+    def error_output(self, environ, start_response):
+        """WSGI mini-app to create error output
+
+        By default, this just uses the 'error_status', 'error_headers',
+        and 'error_body' attributes to generate an output page.  It can
+        be overridden in a subclass to dynamically generate diagnostics,
+        choose an appropriate message for the user's preferred language, etc.
+
+        Note, however, that it's not recommended from a security perspective to
+        spit out diagnostics to any old user; ideally, you should have to do
+        something special to enable diagnostic output, which is why we don't
+        include any here!
+        """
+        start_response(self.error_status,self.error_headers[:],sys.exc_info())
+        return [self.error_body]
+
+
+    # Pure abstract methods; *must* be overridden in subclasses
+
+    def _write(self,data):
+        """Override in subclass to buffer data for send to client
+
+        It's okay if this method actually transmits the data; BaseHandler
+        just separates write and flush operations for greater efficiency
+        when the underlying system actually has such a distinction.
+        """
+        raise NotImplementedError
+
+    def _flush(self):
+        """Override in subclass to force sending of recent '_write()' calls
+
+        It's okay if this method is a no-op (i.e., if '_write()' actually
+        sends the data.
+        """
+        raise NotImplementedError
+
+    def get_stdin(self):
+        """Override in subclass to return suitable 'wsgi.input'"""
+        raise NotImplementedError
+
+    def get_stderr(self):
+        """Override in subclass to return suitable 'wsgi.errors'"""
+        raise NotImplementedError
+
+    def add_cgi_vars(self):
+        """Override in subclass to insert CGI variables in 'self.environ'"""
+        raise NotImplementedError
+
+
+class SimpleHandler(BaseHandler):
+    """Handler that's just initialized with streams, environment, etc.
+
+    This handler subclass is intended for synchronous HTTP/1.0 origin servers,
+    and handles sending the entire response output, given the correct inputs.
+
+    Usage::
+
+        handler = SimpleHandler(
+            inp,out,err,env, multithread=False, multiprocess=True
+        )
+        handler.run(app)"""
+
+    def __init__(self,stdin,stdout,stderr,environ,
+        multithread=True, multiprocess=False
+    ):
+        self.stdin = stdin
+        self.stdout = stdout
+        self.stderr = stderr
+        self.base_env = environ
+        self.wsgi_multithread = multithread
+        self.wsgi_multiprocess = multiprocess
+
+    def get_stdin(self):
+        return self.stdin
+
+    def get_stderr(self):
+        return self.stderr
+
+    def add_cgi_vars(self):
+        self.environ.update(self.base_env)
+
+    def _write(self,data):
+        result = self.stdout.write(data)
+        if result is None or result == len(data):
+            return
+        from warnings import warn
+        warn("SimpleHandler.stdout.write() should not do partial writes",
+            DeprecationWarning)
+        while True:
+            data = data[result:]
+            if not data:
+                break
+            result = self.stdout.write(data)
+
+    def _flush(self):
+        self.stdout.flush()
+        self._flush = self.stdout.flush
+
+
+class BaseCGIHandler(SimpleHandler):
+
+    """CGI-like systems using input/output/error streams and environ mapping
+
+    Usage::
+
+        handler = BaseCGIHandler(inp,out,err,env)
+        handler.run(app)
+
+    This handler class is useful for gateway protocols like ReadyExec and
+    FastCGI, that have usable input/output/error streams and an environment
+    mapping.  It's also the base class for CGIHandler, which just uses
+    sys.stdin, os.environ, and so on.
+
+    The constructor also takes keyword arguments 'multithread' and
+    'multiprocess' (defaulting to 'True' and 'False' respectively) to control
+    the configuration sent to the application.  It sets 'origin_server' to
+    False (to enable CGI-like output), and assumes that 'wsgi.run_once' is
+    False.
+    """
+
+    origin_server = False
+
+
+class CGIHandler(BaseCGIHandler):
+
+    """CGI-based invocation via sys.stdin/stdout/stderr and os.environ
+
+    Usage::
+
+        CGIHandler().run(app)
+
+    The difference between this class and BaseCGIHandler is that it always
+    uses 'wsgi.run_once' of 'True', 'wsgi.multithread' of 'False', and
+    'wsgi.multiprocess' of 'True'.  It does not take any initialization
+    parameters, but always uses 'sys.stdin', 'os.environ', and friends.
+
+    If you need to override any of these parameters, use BaseCGIHandler
+    instead.
+    """
+
+    wsgi_run_once = True
+    # Do not allow os.environ to leak between requests in Google App Engine
+    # and other multi-run CGI use cases.  This is not easily testable.
+    # See http://bugs.python.org/issue7250
+    os_environ = {}
+
+    def __init__(self):
+        BaseCGIHandler.__init__(
+            self, sys.stdin.buffer, sys.stdout.buffer, sys.stderr,
+            read_environ(), multithread=False, multiprocess=True
+        )
+
+
+class IISCGIHandler(BaseCGIHandler):
+    """CGI-based invocation with workaround for IIS path bug
+
+    This handler should be used in preference to CGIHandler when deploying on
+    Microsoft IIS without having set the config allowPathInfo option (IIS>=7)
+    or metabase allowPathInfoForScriptMappings (IIS<7).
+    """
+    wsgi_run_once = True
+    os_environ = {}
+
+    # By default, IIS gives a PATH_INFO that duplicates the SCRIPT_NAME at
+    # the front, causing problems for WSGI applications that wish to implement
+    # routing. This handler strips any such duplicated path.
+
+    # IIS can be configured to pass the correct PATH_INFO, but this causes
+    # another bug where PATH_TRANSLATED is wrong. Luckily this variable is
+    # rarely used and is not guaranteed by WSGI. On IIS<7, though, the
+    # setting can only be made on a vhost level, affecting all other script
+    # mappings, many of which break when exposed to the PATH_TRANSLATED bug.
+    # For this reason IIS<7 is almost never deployed with the fix. (Even IIS7
+    # rarely uses it because there is still no UI for it.)
+
+    # There is no way for CGI code to tell whether the option was set, so a
+    # separate handler class is provided.
+    def __init__(self):
+        environ= read_environ()
+        path = environ.get('PATH_INFO', '')
+        script = environ.get('SCRIPT_NAME', '')
+        if (path+'/').startswith(script+'/'):
+            environ['PATH_INFO'] = path[len(script):]
+        BaseCGIHandler.__init__(
+            self, sys.stdin.buffer, sys.stdout.buffer, sys.stderr,
+            environ, multithread=False, multiprocess=True
+        )
diff --git a/Lib/wsgiref/headers.py b/Lib/wsgiref/headers.py
new file mode 100644
index 000000000..fab851c5a
--- /dev/null
+++ b/Lib/wsgiref/headers.py
@@ -0,0 +1,184 @@
+"""Manage HTTP Response Headers
+
+Much of this module is red-handedly pilfered from email.message in the stdlib,
+so portions are Copyright (C) 2001,2002 Python Software Foundation, and were
+written by Barry Warsaw.
+"""
+
+# Regular expression that matches `special' characters in parameters, the
+# existence of which force quoting of the parameter value.
+import re
+tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
+
+def _formatparam(param, value=None, quote=1):
+    """Convenience function to format and return a key=value pair.
+
+    This will quote the value if needed or if quote is true.
+    """
+    if value is not None and len(value) > 0:
+        if quote or tspecials.search(value):
+            value = value.replace('\\', '\\\\').replace('"', r'\"')
+            return '%s="%s"' % (param, value)
+        else:
+            return '%s=%s' % (param, value)
+    else:
+        return param
+
+
+class Headers:
+    """Manage a collection of HTTP response headers"""
+
+    def __init__(self, headers=None):
+        headers = headers if headers is not None else []
+        if type(headers) is not list:
+            raise TypeError("Headers must be a list of name/value tuples")
+        self._headers = headers
+        if __debug__:
+            for k, v in headers:
+                self._convert_string_type(k)
+                self._convert_string_type(v)
+
+    def _convert_string_type(self, value):
+        """Convert/check value type."""
+        if type(value) is str:
+            return value
+        raise AssertionError("Header names/values must be"
+            " of type str (got {0})".format(repr(value)))
+
+    def __len__(self):
+        """Return the total number of headers, including duplicates."""
+        return len(self._headers)
+
+    def __setitem__(self, name, val):
+        """Set the value of a header."""
+        del self[name]
+        self._headers.append(
+            (self._convert_string_type(name), self._convert_string_type(val)))
+
+    def __delitem__(self,name):
+        """Delete all occurrences of a header, if present.
+
+        Does *not* raise an exception if the header is missing.
+        """
+        name = self._convert_string_type(name.lower())
+        self._headers[:] = [kv for kv in self._headers if kv[0].lower() != name]
+
+    def __getitem__(self,name):
+        """Get the first header value for 'name'
+
+        Return None if the header is missing instead of raising an exception.
+
+        Note that if the header appeared multiple times, the first exactly which
+        occurrence gets returned is undefined.  Use getall() to get all
+        the values matching a header field name.
+        """
+        return self.get(name)
+
+    def __contains__(self, name):
+        """Return true if the message contains the header."""
+        return self.get(name) is not None
+
+
+    def get_all(self, name):
+        """Return a list of all the values for the named field.
+
+        These will be sorted in the order they appeared in the original header
+        list or were added to this instance, and may contain duplicates.  Any
+        fields deleted and re-inserted are always appended to the header list.
+        If no fields exist with the given name, returns an empty list.
+        """
+        name = self._convert_string_type(name.lower())
+        return [kv[1] for kv in self._headers if kv[0].lower()==name]
+
+
+    def get(self,name,default=None):
+        """Get the first header value for 'name', or return 'default'"""
+        name = self._convert_string_type(name.lower())
+        for k,v in self._headers:
+            if k.lower()==name:
+                return v
+        return default
+
+
+    def keys(self):
+        """Return a list of all the header field names.
+
+        These will be sorted in the order they appeared in the original header
+        list, or were added to this instance, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [k for k, v in self._headers]
+
+    def values(self):
+        """Return a list of all header values.
+
+        These will be sorted in the order they appeared in the original header
+        list, or were added to this instance, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [v for k, v in self._headers]
+
+    def items(self):
+        """Get all the header fields and values.
+
+        These will be sorted in the order they were in the original header
+        list, or were added to this instance, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return self._headers[:]
+
+    def __repr__(self):
+        return "%s(%r)" % (self.__class__.__name__, self._headers)
+
+    def __str__(self):
+        """str() returns the formatted headers, complete with end line,
+        suitable for direct HTTP transmission."""
+        return '\r\n'.join(["%s: %s" % kv for kv in self._headers]+['',''])
+
+    def __bytes__(self):
+        return str(self).encode('iso-8859-1')
+
+    def setdefault(self,name,value):
+        """Return first matching header value for 'name', or 'value'
+
+        If there is no header named 'name', add a new header with name 'name'
+        and value 'value'."""
+        result = self.get(name)
+        if result is None:
+            self._headers.append((self._convert_string_type(name),
+                self._convert_string_type(value)))
+            return value
+        else:
+            return result
+
+    def add_header(self, _name, _value, **_params):
+        """Extended header setting.
+
+        _name is the header field to add.  keyword arguments can be used to set
+        additional parameters for the header field, with underscores converted
+        to dashes.  Normally the parameter will be added as key="value" unless
+        value is None, in which case only the key will be added.
+
+        Example:
+
+        h.add_header('content-disposition', 'attachment', filename='bud.gif')
+
+        Note that unlike the corresponding 'email.message' method, this does
+        *not* handle '(charset, language, value)' tuples: all values must be
+        strings or None.
+        """
+        parts = []
+        if _value is not None:
+            _value = self._convert_string_type(_value)
+            parts.append(_value)
+        for k, v in _params.items():
+            k = self._convert_string_type(k)
+            if v is None:
+                parts.append(k.replace('_', '-'))
+            else:
+                v = self._convert_string_type(v)
+                parts.append(_formatparam(k.replace('_', '-'), v))
+        self._headers.append((self._convert_string_type(_name), "; ".join(parts)))
diff --git a/Lib/wsgiref/simple_server.py b/Lib/wsgiref/simple_server.py
new file mode 100644
index 000000000..f71563a5a
--- /dev/null
+++ b/Lib/wsgiref/simple_server.py
@@ -0,0 +1,164 @@
+"""BaseHTTPServer that implements the Python WSGI protocol (PEP 3333)
+
+This is both an example of how WSGI can be implemented, and a basis for running
+simple web applications on a local machine, such as might be done when testing
+or debugging an application.  It has not been reviewed for security issues,
+however, and we strongly recommend that you use a "real" web server for
+production use.
+
+For example usage, see the 'if __name__=="__main__"' block at the end of the
+module.  See also the BaseHTTPServer module docs for other API information.
+"""
+
+from http.server import BaseHTTPRequestHandler, HTTPServer
+import sys
+import urllib.parse
+from wsgiref.handlers import SimpleHandler
+from platform import python_implementation
+
+__version__ = "0.2"
+__all__ = ['WSGIServer', 'WSGIRequestHandler', 'demo_app', 'make_server']
+
+
+server_version = "WSGIServer/" + __version__
+sys_version = python_implementation() + "/" + sys.version.split()[0]
+software_version = server_version + ' ' + sys_version
+
+
+class ServerHandler(SimpleHandler):
+
+    server_software = software_version
+
+    def close(self):
+        try:
+            self.request_handler.log_request(
+                self.status.split(' ',1)[0], self.bytes_sent
+            )
+        finally:
+            SimpleHandler.close(self)
+
+
+
+class WSGIServer(HTTPServer):
+
+    """BaseHTTPServer that implements the Python WSGI protocol"""
+
+    application = None
+
+    def server_bind(self):
+        """Override server_bind to store the server name."""
+        HTTPServer.server_bind(self)
+        self.setup_environ()
+
+    def setup_environ(self):
+        # Set up base environment
+        env = self.base_environ = {}
+        env['SERVER_NAME'] = self.server_name
+        env['GATEWAY_INTERFACE'] = 'CGI/1.1'
+        env['SERVER_PORT'] = str(self.server_port)
+        env['REMOTE_HOST']=''
+        env['CONTENT_LENGTH']=''
+        env['SCRIPT_NAME'] = ''
+
+    def get_app(self):
+        return self.application
+
+    def set_app(self,application):
+        self.application = application
+
+
+
+class WSGIRequestHandler(BaseHTTPRequestHandler):
+
+    server_version = "WSGIServer/" + __version__
+
+    def get_environ(self):
+        env = self.server.base_environ.copy()
+        env['SERVER_PROTOCOL'] = self.request_version
+        env['SERVER_SOFTWARE'] = self.server_version
+        env['REQUEST_METHOD'] = self.command
+        if '?' in self.path:
+            path,query = self.path.split('?',1)
+        else:
+            path,query = self.path,''
+
+        env['PATH_INFO'] = urllib.parse.unquote(path, 'iso-8859-1')
+        env['QUERY_STRING'] = query
+
+        host = self.address_string()
+        if host != self.client_address[0]:
+            env['REMOTE_HOST'] = host
+        env['REMOTE_ADDR'] = self.client_address[0]
+
+        if self.headers.get('content-type') is None:
+            env['CONTENT_TYPE'] = self.headers.get_content_type()
+        else:
+            env['CONTENT_TYPE'] = self.headers['content-type']
+
+        length = self.headers.get('content-length')
+        if length:
+            env['CONTENT_LENGTH'] = length
+
+        for k, v in self.headers.items():
+            k=k.replace('-','_').upper(); v=v.strip()
+            if k in env:
+                continue                    # skip content length, type,etc.
+            if 'HTTP_'+k in env:
+                env['HTTP_'+k] += ','+v     # comma-separate multiple headers
+            else:
+                env['HTTP_'+k] = v
+        return env
+
+    def get_stderr(self):
+        return sys.stderr
+
+    def handle(self):
+        """Handle a single HTTP request"""
+
+        self.raw_requestline = self.rfile.readline(65537)
+        if len(self.raw_requestline) > 65536:
+            self.requestline = ''
+            self.request_version = ''
+            self.command = ''
+            self.send_error(414)
+            return
+
+        if not self.parse_request(): # An error code has been sent, just exit
+            return
+
+        handler = ServerHandler(
+            self.rfile, self.wfile, self.get_stderr(), self.get_environ()
+        )
+        handler.request_handler = self      # backpointer for logging
+        handler.run(self.server.get_app())
+
+
+
+def demo_app(environ,start_response):
+    from io import StringIO
+    stdout = StringIO()
+    print("Hello world!", file=stdout)
+    print(file=stdout)
+    h = sorted(environ.items())
+    for k,v in h:
+        print(k,'=',repr(v), file=stdout)
+    start_response("200 OK", [('Content-Type','text/plain; charset=utf-8')])
+    return [stdout.getvalue().encode("utf-8")]
+
+
+def make_server(
+    host, port, app, server_class=WSGIServer, handler_class=WSGIRequestHandler
+):
+    """Create a new WSGI server listening on `host` and `port` for `app`"""
+    server = server_class((host, port), handler_class)
+    server.set_app(app)
+    return server
+
+
+if __name__ == '__main__':
+    with make_server('', 8000, demo_app) as httpd:
+        sa = httpd.socket.getsockname()
+        print("Serving HTTP on", sa[0], "port", sa[1], "...")
+        import webbrowser
+        webbrowser.open('http://localhost:8000/xyz?abc')
+        httpd.handle_request()  # serve one request, then exit
diff --git a/Lib/wsgiref/util.py b/Lib/wsgiref/util.py
new file mode 100644
index 000000000..516fe898d
--- /dev/null
+++ b/Lib/wsgiref/util.py
@@ -0,0 +1,165 @@
+"""Miscellaneous WSGI-related Utilities"""
+
+import posixpath
+
+__all__ = [
+    'FileWrapper', 'guess_scheme', 'application_uri', 'request_uri',
+    'shift_path_info', 'setup_testing_defaults',
+]
+
+
+class FileWrapper:
+    """Wrapper to convert file-like objects to iterables"""
+
+    def __init__(self, filelike, blksize=8192):
+        self.filelike = filelike
+        self.blksize = blksize
+        if hasattr(filelike,'close'):
+            self.close = filelike.close
+
+    def __getitem__(self,key):
+        data = self.filelike.read(self.blksize)
+        if data:
+            return data
+        raise IndexError
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        data = self.filelike.read(self.blksize)
+        if data:
+            return data
+        raise StopIteration
+
+def guess_scheme(environ):
+    """Return a guess for whether 'wsgi.url_scheme' should be 'http' or 'https'
+    """
+    if environ.get("HTTPS") in ('yes','on','1'):
+        return 'https'
+    else:
+        return 'http'
+
+def application_uri(environ):
+    """Return the application's base URI (no PATH_INFO or QUERY_STRING)"""
+    url = environ['wsgi.url_scheme']+'://'
+    from urllib.parse import quote
+
+    if environ.get('HTTP_HOST'):
+        url += environ['HTTP_HOST']
+    else:
+        url += environ['SERVER_NAME']
+
+        if environ['wsgi.url_scheme'] == 'https':
+            if environ['SERVER_PORT'] != '443':
+                url += ':' + environ['SERVER_PORT']
+        else:
+            if environ['SERVER_PORT'] != '80':
+                url += ':' + environ['SERVER_PORT']
+
+    url += quote(environ.get('SCRIPT_NAME') or '/', encoding='latin1')
+    return url
+
+def request_uri(environ, include_query=True):
+    """Return the full request URI, optionally including the query string"""
+    url = application_uri(environ)
+    from urllib.parse import quote
+    path_info = quote(environ.get('PATH_INFO',''), safe='/;=,', encoding='latin1')
+    if not environ.get('SCRIPT_NAME'):
+        url += path_info[1:]
+    else:
+        url += path_info
+    if include_query and environ.get('QUERY_STRING'):
+        url += '?' + environ['QUERY_STRING']
+    return url
+
+def shift_path_info(environ):
+    """Shift a name from PATH_INFO to SCRIPT_NAME, returning it
+
+    If there are no remaining path segments in PATH_INFO, return None.
+    Note: 'environ' is modified in-place; use a copy if you need to keep
+    the original PATH_INFO or SCRIPT_NAME.
+
+    Note: when PATH_INFO is just a '/', this returns '' and appends a trailing
+    '/' to SCRIPT_NAME, even though empty path segments are normally ignored,
+    and SCRIPT_NAME doesn't normally end in a '/'.  This is intentional
+    behavior, to ensure that an application can tell the difference between
+    '/x' and '/x/' when traversing to objects.
+    """
+    path_info = environ.get('PATH_INFO','')
+    if not path_info:
+        return None
+
+    path_parts = path_info.split('/')
+    path_parts[1:-1] = [p for p in path_parts[1:-1] if p and p != '.']
+    name = path_parts[1]
+    del path_parts[1]
+
+    script_name = environ.get('SCRIPT_NAME','')
+    script_name = posixpath.normpath(script_name+'/'+name)
+    if script_name.endswith('/'):
+        script_name = script_name[:-1]
+    if not name and not script_name.endswith('/'):
+        script_name += '/'
+
+    environ['SCRIPT_NAME'] = script_name
+    environ['PATH_INFO']   = '/'.join(path_parts)
+
+    # Special case: '/.' on PATH_INFO doesn't get stripped,
+    # because we don't strip the last element of PATH_INFO
+    # if there's only one path part left.  Instead of fixing this
+    # above, we fix it here so that PATH_INFO gets normalized to
+    # an empty string in the environ.
+    if name=='.':
+        name = None
+    return name
+
+def setup_testing_defaults(environ):
+    """Update 'environ' with trivial defaults for testing purposes
+
+    This adds various parameters required for WSGI, including HTTP_HOST,
+    SERVER_NAME, SERVER_PORT, REQUEST_METHOD, SCRIPT_NAME, PATH_INFO,
+    and all of the wsgi.* variables.  It only supplies default values,
+    and does not replace any existing settings for these variables.
+
+    This routine is intended to make it easier for unit tests of WSGI
+    servers and applications to set up dummy environments.  It should *not*
+    be used by actual WSGI servers or applications, since the data is fake!
+    """
+
+    environ.setdefault('SERVER_NAME','127.0.0.1')
+    environ.setdefault('SERVER_PROTOCOL','HTTP/1.0')
+
+    environ.setdefault('HTTP_HOST',environ['SERVER_NAME'])
+    environ.setdefault('REQUEST_METHOD','GET')
+
+    if 'SCRIPT_NAME' not in environ and 'PATH_INFO' not in environ:
+        environ.setdefault('SCRIPT_NAME','')
+        environ.setdefault('PATH_INFO','/')
+
+    environ.setdefault('wsgi.version', (1,0))
+    environ.setdefault('wsgi.run_once', 0)
+    environ.setdefault('wsgi.multithread', 0)
+    environ.setdefault('wsgi.multiprocess', 0)
+
+    from io import StringIO, BytesIO
+    environ.setdefault('wsgi.input', BytesIO())
+    environ.setdefault('wsgi.errors', StringIO())
+    environ.setdefault('wsgi.url_scheme',guess_scheme(environ))
+
+    if environ['wsgi.url_scheme']=='http':
+        environ.setdefault('SERVER_PORT', '80')
+    elif environ['wsgi.url_scheme']=='https':
+        environ.setdefault('SERVER_PORT', '443')
+
+
+
+_hoppish = {
+    'connection':1, 'keep-alive':1, 'proxy-authenticate':1,
+    'proxy-authorization':1, 'te':1, 'trailers':1, 'transfer-encoding':1,
+    'upgrade':1
+}.__contains__
+
+def is_hop_by_hop(header_name):
+    """Return true if 'header_name' is an HTTP/1.1 "Hop-by-Hop" header"""
+    return _hoppish(header_name.lower())
diff --git a/Lib/wsgiref/validate.py b/Lib/wsgiref/validate.py
new file mode 100644
index 000000000..6107dcd7a
--- /dev/null
+++ b/Lib/wsgiref/validate.py
@@ -0,0 +1,443 @@
+# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
+# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
+# Also licenced under the Apache License, 2.0: http://opensource.org/licenses/apache2.0.php
+# Licensed to PSF under a Contributor Agreement
+"""
+Middleware to check for obedience to the WSGI specification.
+
+Some of the things this checks:
+
+* Signature of the application and start_response (including that
+  keyword arguments are not used).
+
+* Environment checks:
+
+  - Environment is a dictionary (and not a subclass).
+
+  - That all the required keys are in the environment: REQUEST_METHOD,
+    SERVER_NAME, SERVER_PORT, wsgi.version, wsgi.input, wsgi.errors,
+    wsgi.multithread, wsgi.multiprocess, wsgi.run_once
+
+  - That HTTP_CONTENT_TYPE and HTTP_CONTENT_LENGTH are not in the
+    environment (these headers should appear as CONTENT_LENGTH and
+    CONTENT_TYPE).
+
+  - Warns if QUERY_STRING is missing, as the cgi module acts
+    unpredictably in that case.
+
+  - That CGI-style variables (that don't contain a .) have
+    (non-unicode) string values
+
+  - That wsgi.version is a tuple
+
+  - That wsgi.url_scheme is 'http' or 'https' (@@: is this too
+    restrictive?)
+
+  - Warns if the REQUEST_METHOD is not known (@@: probably too
+    restrictive).
+
+  - That SCRIPT_NAME and PATH_INFO are empty or start with /
+
+  - That at least one of SCRIPT_NAME or PATH_INFO are set.
+
+  - That CONTENT_LENGTH is a positive integer.
+
+  - That SCRIPT_NAME is not '/' (it should be '', and PATH_INFO should
+    be '/').
+
+  - That wsgi.input has the methods read, readline, readlines, and
+    __iter__
+
+  - That wsgi.errors has the methods flush, write, writelines
+
+* The status is a string, contains a space, starts with an integer,
+  and that integer is in range (> 100).
+
+* That the headers is a list (not a subclass, not another kind of
+  sequence).
+
+* That the items of the headers are tuples of strings.
+
+* That there is no 'status' header (that is used in CGI, but not in
+  WSGI).
+
+* That the headers don't contain newlines or colons, end in _ or -, or
+  contain characters codes below 037.
+
+* That Content-Type is given if there is content (CGI often has a
+  default content type, but WSGI does not).
+
+* That no Content-Type is given when there is no content (@@: is this
+  too restrictive?)
+
+* That the exc_info argument to start_response is a tuple or None.
+
+* That all calls to the writer are with strings, and no other methods
+  on the writer are accessed.
+
+* That wsgi.input is used properly:
+
+  - .read() is called with zero or one argument
+
+  - That it returns a string
+
+  - That readline, readlines, and __iter__ return strings
+
+  - That .close() is not called
+
+  - No other methods are provided
+
+* That wsgi.errors is used properly:
+
+  - .write() and .writelines() is called with a string
+
+  - That .close() is not called, and no other methods are provided.
+
+* The response iterator:
+
+  - That it is not a string (it should be a list of a single string; a
+    string will work, but perform horribly).
+
+  - That .__next__() returns a string
+
+  - That the iterator is not iterated over until start_response has
+    been called (that can signal either a server or application
+    error).
+
+  - That .close() is called (doesn't raise exception, only prints to
+    sys.stderr, because we only know it isn't called when the object
+    is garbage collected).
+"""
+__all__ = ['validator']
+
+
+import re
+import sys
+import warnings
+
+header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$')
+bad_header_value_re = re.compile(r'[\000-\037]')
+
+class WSGIWarning(Warning):
+    """
+    Raised in response to WSGI-spec-related warnings
+    """
+
+def assert_(cond, *args):
+    if not cond:
+        raise AssertionError(*args)
+
+def check_string_type(value, title):
+    if type (value) is str:
+        return value
+    raise AssertionError(
+        "{0} must be of type str (got {1})".format(title, repr(value)))
+
+def validator(application):
+
+    """
+    When applied between a WSGI server and a WSGI application, this
+    middleware will check for WSGI compliancy on a number of levels.
+    This middleware does not modify the request or response in any
+    way, but will raise an AssertionError if anything seems off
+    (except for a failure to close the application iterator, which
+    will be printed to stderr -- there's no way to raise an exception
+    at that point).
+    """
+
+    def lint_app(*args, **kw):
+        assert_(len(args) == 2, "Two arguments required")
+        assert_(not kw, "No keyword arguments allowed")
+        environ, start_response = args
+
+        check_environ(environ)
+
+        # We use this to check if the application returns without
+        # calling start_response:
+        start_response_started = []
+
+        def start_response_wrapper(*args, **kw):
+            assert_(len(args) == 2 or len(args) == 3, (
+                "Invalid number of arguments: %s" % (args,)))
+            assert_(not kw, "No keyword arguments allowed")
+            status = args[0]
+            headers = args[1]
+            if len(args) == 3:
+                exc_info = args[2]
+            else:
+                exc_info = None
+
+            check_status(status)
+            check_headers(headers)
+            check_content_type(status, headers)
+            check_exc_info(exc_info)
+
+            start_response_started.append(None)
+            return WriteWrapper(start_response(*args))
+
+        environ['wsgi.input'] = InputWrapper(environ['wsgi.input'])
+        environ['wsgi.errors'] = ErrorWrapper(environ['wsgi.errors'])
+
+        iterator = application(environ, start_response_wrapper)
+        assert_(iterator is not None and iterator != False,
+            "The application must return an iterator, if only an empty list")
+
+        check_iterator(iterator)
+
+        return IteratorWrapper(iterator, start_response_started)
+
+    return lint_app
+
+class InputWrapper:
+
+    def __init__(self, wsgi_input):
+        self.input = wsgi_input
+
+    def read(self, *args):
+        assert_(len(args) == 1)
+        v = self.input.read(*args)
+        assert_(type(v) is bytes)
+        return v
+
+    def readline(self, *args):
+        assert_(len(args) <= 1)
+        v = self.input.readline(*args)
+        assert_(type(v) is bytes)
+        return v
+
+    def readlines(self, *args):
+        assert_(len(args) <= 1)
+        lines = self.input.readlines(*args)
+        assert_(type(lines) is list)
+        for line in lines:
+            assert_(type(line) is bytes)
+        return lines
+
+    def __iter__(self):
+        while 1:
+            line = self.readline()
+            if not line:
+                return
+            yield line
+
+    def close(self):
+        assert_(0, "input.close() must not be called")
+
+class ErrorWrapper:
+
+    def __init__(self, wsgi_errors):
+        self.errors = wsgi_errors
+
+    def write(self, s):
+        assert_(type(s) is str)
+        self.errors.write(s)
+
+    def flush(self):
+        self.errors.flush()
+
+    def writelines(self, seq):
+        for line in seq:
+            self.write(line)
+
+    def close(self):
+        assert_(0, "errors.close() must not be called")
+
+class WriteWrapper:
+
+    def __init__(self, wsgi_writer):
+        self.writer = wsgi_writer
+
+    def __call__(self, s):
+        assert_(type(s) is bytes)
+        self.writer(s)
+
+class PartialIteratorWrapper:
+
+    def __init__(self, wsgi_iterator):
+        self.iterator = wsgi_iterator
+
+    def __iter__(self):
+        # We want to make sure __iter__ is called
+        return IteratorWrapper(self.iterator, None)
+
+class IteratorWrapper:
+
+    def __init__(self, wsgi_iterator, check_start_response):
+        self.original_iterator = wsgi_iterator
+        self.iterator = iter(wsgi_iterator)
+        self.closed = False
+        self.check_start_response = check_start_response
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        assert_(not self.closed,
+            "Iterator read after closed")
+        v = next(self.iterator)
+        if type(v) is not bytes:
+            assert_(False, "Iterator yielded non-bytestring (%r)" % (v,))
+        if self.check_start_response is not None:
+            assert_(self.check_start_response,
+                "The application returns and we started iterating over its body, but start_response has not yet been called")
+            self.check_start_response = None
+        return v
+
+    def close(self):
+        self.closed = True
+        if hasattr(self.original_iterator, 'close'):
+            self.original_iterator.close()
+
+    def __del__(self):
+        if not self.closed:
+            sys.stderr.write(
+                "Iterator garbage collected without being closed")
+        assert_(self.closed,
+            "Iterator garbage collected without being closed")
+
+def check_environ(environ):
+    assert_(type(environ) is dict,
+        "Environment is not of the right type: %r (environment: %r)"
+        % (type(environ), environ))
+
+    for key in ['REQUEST_METHOD', 'SERVER_NAME', 'SERVER_PORT',
+                'wsgi.version', 'wsgi.input', 'wsgi.errors',
+                'wsgi.multithread', 'wsgi.multiprocess',
+                'wsgi.run_once']:
+        assert_(key in environ,
+            "Environment missing required key: %r" % (key,))
+
+    for key in ['HTTP_CONTENT_TYPE', 'HTTP_CONTENT_LENGTH']:
+        assert_(key not in environ,
+            "Environment should not have the key: %s "
+            "(use %s instead)" % (key, key[5:]))
+
+    if 'QUERY_STRING' not in environ:
+        warnings.warn(
+            'QUERY_STRING is not in the WSGI environment; the cgi '
+            'module will use sys.argv when this variable is missing, '
+            'so application errors are more likely',
+            WSGIWarning)
+
+    for key in environ.keys():
+        if '.' in key:
+            # Extension, we don't care about its type
+            continue
+        assert_(type(environ[key]) is str,
+            "Environmental variable %s is not a string: %r (value: %r)"
+            % (key, type(environ[key]), environ[key]))
+
+    assert_(type(environ['wsgi.version']) is tuple,
+        "wsgi.version should be a tuple (%r)" % (environ['wsgi.version'],))
+    assert_(environ['wsgi.url_scheme'] in ('http', 'https'),
+        "wsgi.url_scheme unknown: %r" % environ['wsgi.url_scheme'])
+
+    check_input(environ['wsgi.input'])
+    check_errors(environ['wsgi.errors'])
+
+    # @@: these need filling out:
+    if environ['REQUEST_METHOD'] not in (
+        'GET', 'HEAD', 'POST', 'OPTIONS', 'PATCH', 'PUT', 'DELETE', 'TRACE'):
+        warnings.warn(
+            "Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'],
+            WSGIWarning)
+
+    assert_(not environ.get('SCRIPT_NAME')
+            or environ['SCRIPT_NAME'].startswith('/'),
+        "SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME'])
+    assert_(not environ.get('PATH_INFO')
+            or environ['PATH_INFO'].startswith('/'),
+        "PATH_INFO doesn't start with /: %r" % environ['PATH_INFO'])
+    if environ.get('CONTENT_LENGTH'):
+        assert_(int(environ['CONTENT_LENGTH']) >= 0,
+            "Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH'])
+
+    if not environ.get('SCRIPT_NAME'):
+        assert_('PATH_INFO' in environ,
+            "One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO "
+            "should at least be '/' if SCRIPT_NAME is empty)")
+    assert_(environ.get('SCRIPT_NAME') != '/',
+        "SCRIPT_NAME cannot be '/'; it should instead be '', and "
+        "PATH_INFO should be '/'")
+
+def check_input(wsgi_input):
+    for attr in ['read', 'readline', 'readlines', '__iter__']:
+        assert_(hasattr(wsgi_input, attr),
+            "wsgi.input (%r) doesn't have the attribute %s"
+            % (wsgi_input, attr))
+
+def check_errors(wsgi_errors):
+    for attr in ['flush', 'write', 'writelines']:
+        assert_(hasattr(wsgi_errors, attr),
+            "wsgi.errors (%r) doesn't have the attribute %s"
+            % (wsgi_errors, attr))
+
+def check_status(status):
+    status = check_string_type(status, "Status")
+    # Implicitly check that we can turn it into an integer:
+    status_code = status.split(None, 1)[0]
+    assert_(len(status_code) == 3,
+        "Status codes must be three characters: %r" % status_code)
+    status_int = int(status_code)
+    assert_(status_int >= 100, "Status code is invalid: %r" % status_int)
+    if len(status) < 4 or status[3] != ' ':
+        warnings.warn(
+            "The status string (%r) should be a three-digit integer "
+            "followed by a single space and a status explanation"
+            % status, WSGIWarning)
+
+def check_headers(headers):
+    assert_(type(headers) is list,
+        "Headers (%r) must be of type list: %r"
+        % (headers, type(headers)))
+    header_names = {}
+    for item in headers:
+        assert_(type(item) is tuple,
+            "Individual headers (%r) must be of type tuple: %r"
+            % (item, type(item)))
+        assert_(len(item) == 2)
+        name, value = item
+        name = check_string_type(name, "Header name")
+        value = check_string_type(value, "Header value")
+        assert_(name.lower() != 'status',
+            "The Status header cannot be used; it conflicts with CGI "
+            "script, and HTTP status is not given through headers "
+            "(value: %r)." % value)
+        header_names[name.lower()] = None
+        assert_('\n' not in name and ':' not in name,
+            "Header names may not contain ':' or '\\n': %r" % name)
+        assert_(header_re.search(name), "Bad header name: %r" % name)
+        assert_(not name.endswith('-') and not name.endswith('_'),
+            "Names may not end in '-' or '_': %r" % name)
+        if bad_header_value_re.search(value):
+            assert_(0, "Bad header value: %r (bad char: %r)"
+            % (value, bad_header_value_re.search(value).group(0)))
+
+def check_content_type(status, headers):
+    status = check_string_type(status, "Status")
+    code = int(status.split(None, 1)[0])
+    # @@: need one more person to verify this interpretation of RFC 2616
+    #     http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
+    NO_MESSAGE_BODY = (204, 304)
+    for name, value in headers:
+        name = check_string_type(name, "Header name")
+        if name.lower() == 'content-type':
+            if code not in NO_MESSAGE_BODY:
+                return
+            assert_(0, ("Content-Type header found in a %s response, "
+                        "which must not return content.") % code)
+    if code not in NO_MESSAGE_BODY:
+        assert_(0, "No Content-Type header found in headers (%s)" % headers)
+
+def check_exc_info(exc_info):
+    assert_(exc_info is None or type(exc_info) is tuple,
+        "exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info)))
+    # More exc_info checks?
+
+def check_iterator(iterator):
+    # Technically a bytestring is legal, which is why it's a really bad
+    # idea, because it may cause the response to be returned
+    # character-by-character
+    assert_(not isinstance(iterator, (str, bytes)),
+        "You should not return a string as your application iterator, "
+        "instead return a single-item list containing a bytestring.")
diff --git a/Lib/xml/__init__.py b/Lib/xml/__init__.py
new file mode 100644
index 000000000..bf6d8ddfd
--- /dev/null
+++ b/Lib/xml/__init__.py
@@ -0,0 +1,20 @@
+"""Core XML support for Python.
+
+This package contains four sub-packages:
+
+dom -- The W3C Document Object Model.  This supports DOM Level 1 +
+       Namespaces.
+
+parsers -- Python wrappers for XML parsers (currently only supports Expat).
+
+sax -- The Simple API for XML, developed by XML-Dev, led by David
+       Megginson and ported to Python by Lars Marius Garshol.  This
+       supports the SAX 2 API.
+
+etree -- The ElementTree XML library.  This is a subset of the full
+       ElementTree XML release.
+
+"""
+
+
+__all__ = ["dom", "parsers", "sax", "etree"]
diff --git a/Lib/xml/dom/NodeFilter.py b/Lib/xml/dom/NodeFilter.py
new file mode 100644
index 000000000..640e0bfd2
--- /dev/null
+++ b/Lib/xml/dom/NodeFilter.py
@@ -0,0 +1,27 @@
+# This is the Python mapping for interface NodeFilter from
+# DOM2-Traversal-Range. It contains only constants.
+
+class NodeFilter:
+    """
+    This is the DOM2 NodeFilter interface. It contains only constants.
+    """
+    FILTER_ACCEPT = 1
+    FILTER_REJECT = 2
+    FILTER_SKIP   = 3
+
+    SHOW_ALL                    = 0xFFFFFFFF
+    SHOW_ELEMENT                = 0x00000001
+    SHOW_ATTRIBUTE              = 0x00000002
+    SHOW_TEXT                   = 0x00000004
+    SHOW_CDATA_SECTION          = 0x00000008
+    SHOW_ENTITY_REFERENCE       = 0x00000010
+    SHOW_ENTITY                 = 0x00000020
+    SHOW_PROCESSING_INSTRUCTION = 0x00000040
+    SHOW_COMMENT                = 0x00000080
+    SHOW_DOCUMENT               = 0x00000100
+    SHOW_DOCUMENT_TYPE          = 0x00000200
+    SHOW_DOCUMENT_FRAGMENT      = 0x00000400
+    SHOW_NOTATION               = 0x00000800
+
+    def acceptNode(self, node):
+        raise NotImplementedError
diff --git a/Lib/xml/dom/__init__.py b/Lib/xml/dom/__init__.py
new file mode 100644
index 000000000..97cf9a642
--- /dev/null
+++ b/Lib/xml/dom/__init__.py
@@ -0,0 +1,140 @@
+"""W3C Document Object Model implementation for Python.
+
+The Python mapping of the Document Object Model is documented in the
+Python Library Reference in the section on the xml.dom package.
+
+This package contains the following modules:
+
+minidom -- A simple implementation of the Level 1 DOM with namespace
+           support added (based on the Level 2 specification) and other
+           minor Level 2 functionality.
+
+pulldom -- DOM builder supporting on-demand tree-building for selected
+           subtrees of the document.
+
+"""
+
+
+class Node:
+    """Class giving the NodeType constants."""
+    __slots__ = ()
+
+    # DOM implementations may use this as a base class for their own
+    # Node implementations.  If they don't, the constants defined here
+    # should still be used as the canonical definitions as they match
+    # the values given in the W3C recommendation.  Client code can
+    # safely refer to these values in all tests of Node.nodeType
+    # values.
+
+    ELEMENT_NODE                = 1
+    ATTRIBUTE_NODE              = 2
+    TEXT_NODE                   = 3
+    CDATA_SECTION_NODE          = 4
+    ENTITY_REFERENCE_NODE       = 5
+    ENTITY_NODE                 = 6
+    PROCESSING_INSTRUCTION_NODE = 7
+    COMMENT_NODE                = 8
+    DOCUMENT_NODE               = 9
+    DOCUMENT_TYPE_NODE          = 10
+    DOCUMENT_FRAGMENT_NODE      = 11
+    NOTATION_NODE               = 12
+
+
+#ExceptionCode
+INDEX_SIZE_ERR                 = 1
+DOMSTRING_SIZE_ERR             = 2
+HIERARCHY_REQUEST_ERR          = 3
+WRONG_DOCUMENT_ERR             = 4
+INVALID_CHARACTER_ERR          = 5
+NO_DATA_ALLOWED_ERR            = 6
+NO_MODIFICATION_ALLOWED_ERR    = 7
+NOT_FOUND_ERR                  = 8
+NOT_SUPPORTED_ERR              = 9
+INUSE_ATTRIBUTE_ERR            = 10
+INVALID_STATE_ERR              = 11
+SYNTAX_ERR                     = 12
+INVALID_MODIFICATION_ERR       = 13
+NAMESPACE_ERR                  = 14
+INVALID_ACCESS_ERR             = 15
+VALIDATION_ERR                 = 16
+
+
+class DOMException(Exception):
+    """Abstract base class for DOM exceptions.
+    Exceptions with specific codes are specializations of this class."""
+
+    def __init__(self, *args, **kw):
+        if self.__class__ is DOMException:
+            raise RuntimeError(
+                "DOMException should not be instantiated directly")
+        Exception.__init__(self, *args, **kw)
+
+    def _get_code(self):
+        return self.code
+
+
+class IndexSizeErr(DOMException):
+    code = INDEX_SIZE_ERR
+
+class DomstringSizeErr(DOMException):
+    code = DOMSTRING_SIZE_ERR
+
+class HierarchyRequestErr(DOMException):
+    code = HIERARCHY_REQUEST_ERR
+
+class WrongDocumentErr(DOMException):
+    code = WRONG_DOCUMENT_ERR
+
+class InvalidCharacterErr(DOMException):
+    code = INVALID_CHARACTER_ERR
+
+class NoDataAllowedErr(DOMException):
+    code = NO_DATA_ALLOWED_ERR
+
+class NoModificationAllowedErr(DOMException):
+    code = NO_MODIFICATION_ALLOWED_ERR
+
+class NotFoundErr(DOMException):
+    code = NOT_FOUND_ERR
+
+class NotSupportedErr(DOMException):
+    code = NOT_SUPPORTED_ERR
+
+class InuseAttributeErr(DOMException):
+    code = INUSE_ATTRIBUTE_ERR
+
+class InvalidStateErr(DOMException):
+    code = INVALID_STATE_ERR
+
+class SyntaxErr(DOMException):
+    code = SYNTAX_ERR
+
+class InvalidModificationErr(DOMException):
+    code = INVALID_MODIFICATION_ERR
+
+class NamespaceErr(DOMException):
+    code = NAMESPACE_ERR
+
+class InvalidAccessErr(DOMException):
+    code = INVALID_ACCESS_ERR
+
+class ValidationErr(DOMException):
+    code = VALIDATION_ERR
+
+class UserDataHandler:
+    """Class giving the operation constants for UserDataHandler.handle()."""
+
+    # Based on DOM Level 3 (WD 9 April 2002)
+
+    NODE_CLONED   = 1
+    NODE_IMPORTED = 2
+    NODE_DELETED  = 3
+    NODE_RENAMED  = 4
+
+XML_NAMESPACE = "http://www.w3.org/XML/1998/namespace"
+XMLNS_NAMESPACE = "http://www.w3.org/2000/xmlns/"
+XHTML_NAMESPACE = "http://www.w3.org/1999/xhtml"
+EMPTY_NAMESPACE = None
+EMPTY_PREFIX = None
+
+from .domreg import getDOMImplementation, registerDOMImplementation
diff --git a/Lib/xml/dom/domreg.py b/Lib/xml/dom/domreg.py
new file mode 100644
index 000000000..69c17eebb
--- /dev/null
+++ b/Lib/xml/dom/domreg.py
@@ -0,0 +1,99 @@
+"""Registration facilities for DOM. This module should not be used
+directly. Instead, the functions getDOMImplementation and
+registerDOMImplementation should be imported from xml.dom."""
+
+# This is a list of well-known implementations.  Well-known names
+# should be published by posting to xml-sig@python.org, and are
+# subsequently recorded in this file.
+
+import sys
+
+well_known_implementations = {
+    'minidom':'xml.dom.minidom',
+    '4DOM': 'xml.dom.DOMImplementation',
+    }
+
+# DOM implementations not officially registered should register
+# themselves with their
+
+registered = {}
+
+def registerDOMImplementation(name, factory):
+    """registerDOMImplementation(name, factory)
+
+    Register the factory function with the name. The factory function
+    should return an object which implements the DOMImplementation
+    interface. The factory function can either return the same object,
+    or a new one (e.g. if that implementation supports some
+    customization)."""
+
+    registered[name] = factory
+
+def _good_enough(dom, features):
+    "_good_enough(dom, features) -> Return 1 if the dom offers the features"
+    for f,v in features:
+        if not dom.hasFeature(f,v):
+            return 0
+    return 1
+
+def getDOMImplementation(name=None, features=()):
+    """getDOMImplementation(name = None, features = ()) -> DOM implementation.
+
+    Return a suitable DOM implementation. The name is either
+    well-known, the module name of a DOM implementation, or None. If
+    it is not None, imports the corresponding module and returns
+    DOMImplementation object if the import succeeds.
+
+    If name is not given, consider the available implementations to
+    find one with the required feature set. If no implementation can
+    be found, raise an ImportError. The features list must be a sequence
+    of (feature, version) pairs which are passed to hasFeature."""
+
+    import os
+    creator = None
+    mod = well_known_implementations.get(name)
+    if mod:
+        mod = __import__(mod, {}, {}, ['getDOMImplementation'])
+        return mod.getDOMImplementation()
+    elif name:
+        return registered[name]()
+    elif not sys.flags.ignore_environment and "PYTHON_DOM" in os.environ:
+        return getDOMImplementation(name = os.environ["PYTHON_DOM"])
+
+    # User did not specify a name, try implementations in arbitrary
+    # order, returning the one that has the required features
+    if isinstance(features, str):
+        features = _parse_feature_string(features)
+    for creator in registered.values():
+        dom = creator()
+        if _good_enough(dom, features):
+            return dom
+
+    for creator in well_known_implementations.keys():
+        try:
+            dom = getDOMImplementation(name = creator)
+        except Exception: # typically ImportError, or AttributeError
+            continue
+        if _good_enough(dom, features):
+            return dom
+
+    raise ImportError("no suitable DOM implementation found")
+
+def _parse_feature_string(s):
+    features = []
+    parts = s.split()
+    i = 0
+    length = len(parts)
+    while i < length:
+        feature = parts[i]
+        if feature[0] in "0123456789":
+            raise ValueError("bad feature name: %r" % (feature,))
+        i = i + 1
+        version = None
+        if i < length:
+            v = parts[i]
+            if v[0] in "0123456789":
+                i = i + 1
+                version = v
+        features.append((feature, version))
+    return tuple(features)
diff --git a/Lib/xml/dom/expatbuilder.py b/Lib/xml/dom/expatbuilder.py
new file mode 100644
index 000000000..2bd835b03
--- /dev/null
+++ b/Lib/xml/dom/expatbuilder.py
@@ -0,0 +1,965 @@
+"""Facility to use the Expat parser to load a minidom instance
+from a string or file.
+
+This avoids all the overhead of SAX and pulldom to gain performance.
+"""
+
+# Warning!
+#
+# This module is tightly bound to the implementation details of the
+# minidom DOM and can't be used with other DOM implementations.  This
+# is due, in part, to a lack of appropriate methods in the DOM (there is
+# no way to create Entity and Notation nodes via the DOM Level 2
+# interface), and for performance.  The latter is the cause of some fairly
+# cryptic code.
+#
+# Performance hacks:
+#
+#   -  .character_data_handler() has an extra case in which continuing
+#      data is appended to an existing Text node; this can be a
+#      speedup since pyexpat can break up character data into multiple
+#      callbacks even though we set the buffer_text attribute on the
+#      parser.  This also gives us the advantage that we don't need a
+#      separate normalization pass.
+#
+#   -  Determining that a node exists is done using an identity comparison
+#      with None rather than a truth test; this avoids searching for and
+#      calling any methods on the node object if it exists.  (A rather
+#      nice speedup is achieved this way as well!)
+
+from xml.dom import xmlbuilder, minidom, Node
+from xml.dom import EMPTY_NAMESPACE, EMPTY_PREFIX, XMLNS_NAMESPACE
+from xml.parsers import expat
+from xml.dom.minidom import _append_child, _set_attribute_node
+from xml.dom.NodeFilter import NodeFilter
+
+TEXT_NODE = Node.TEXT_NODE
+CDATA_SECTION_NODE = Node.CDATA_SECTION_NODE
+DOCUMENT_NODE = Node.DOCUMENT_NODE
+
+FILTER_ACCEPT = xmlbuilder.DOMBuilderFilter.FILTER_ACCEPT
+FILTER_REJECT = xmlbuilder.DOMBuilderFilter.FILTER_REJECT
+FILTER_SKIP = xmlbuilder.DOMBuilderFilter.FILTER_SKIP
+FILTER_INTERRUPT = xmlbuilder.DOMBuilderFilter.FILTER_INTERRUPT
+
+theDOMImplementation = minidom.getDOMImplementation()
+
+# Expat typename -> TypeInfo
+_typeinfo_map = {
+    "CDATA":    minidom.TypeInfo(None, "cdata"),
+    "ENUM":     minidom.TypeInfo(None, "enumeration"),
+    "ENTITY":   minidom.TypeInfo(None, "entity"),
+    "ENTITIES": minidom.TypeInfo(None, "entities"),
+    "ID":       minidom.TypeInfo(None, "id"),
+    "IDREF":    minidom.TypeInfo(None, "idref"),
+    "IDREFS":   minidom.TypeInfo(None, "idrefs"),
+    "NMTOKEN":  minidom.TypeInfo(None, "nmtoken"),
+    "NMTOKENS": minidom.TypeInfo(None, "nmtokens"),
+    }
+
+class ElementInfo(object):
+    __slots__ = '_attr_info', '_model', 'tagName'
+
+    def __init__(self, tagName, model=None):
+        self.tagName = tagName
+        self._attr_info = []
+        self._model = model
+
+    def __getstate__(self):
+        return self._attr_info, self._model, self.tagName
+
+    def __setstate__(self, state):
+        self._attr_info, self._model, self.tagName = state
+
+    def getAttributeType(self, aname):
+        for info in self._attr_info:
+            if info[1] == aname:
+                t = info[-2]
+                if t[0] == "(":
+                    return _typeinfo_map["ENUM"]
+                else:
+                    return _typeinfo_map[info[-2]]
+        return minidom._no_type
+
+    def getAttributeTypeNS(self, namespaceURI, localName):
+        return minidom._no_type
+
+    def isElementContent(self):
+        if self._model:
+            type = self._model[0]
+            return type not in (expat.model.XML_CTYPE_ANY,
+                                expat.model.XML_CTYPE_MIXED)
+        else:
+            return False
+
+    def isEmpty(self):
+        if self._model:
+            return self._model[0] == expat.model.XML_CTYPE_EMPTY
+        else:
+            return False
+
+    def isId(self, aname):
+        for info in self._attr_info:
+            if info[1] == aname:
+                return info[-2] == "ID"
+        return False
+
+    def isIdNS(self, euri, ename, auri, aname):
+        # not sure this is meaningful
+        return self.isId((auri, aname))
+
+def _intern(builder, s):
+    return builder._intern_setdefault(s, s)
+
+def _parse_ns_name(builder, name):
+    assert ' ' in name
+    parts = name.split(' ')
+    intern = builder._intern_setdefault
+    if len(parts) == 3:
+        uri, localname, prefix = parts
+        prefix = intern(prefix, prefix)
+        qname = "%s:%s" % (prefix, localname)
+        qname = intern(qname, qname)
+        localname = intern(localname, localname)
+    elif len(parts) == 2:
+        uri, localname = parts
+        prefix = EMPTY_PREFIX
+        qname = localname = intern(localname, localname)
+    else:
+        raise ValueError("Unsupported syntax: spaces in URIs not supported: %r" % name)
+    return intern(uri, uri), localname, prefix, qname
+
+
+class ExpatBuilder:
+    """Document builder that uses Expat to build a ParsedXML.DOM document
+    instance."""
+
+    def __init__(self, options=None):
+        if options is None:
+            options = xmlbuilder.Options()
+        self._options = options
+        if self._options.filter is not None:
+            self._filter = FilterVisibilityController(self._options.filter)
+        else:
+            self._filter = None
+            # This *really* doesn't do anything in this case, so
+            # override it with something fast & minimal.
+            self._finish_start_element = id
+        self._parser = None
+        self.reset()
+
+    def createParser(self):
+        """Create a new parser object."""
+        return expat.ParserCreate()
+
+    def getParser(self):
+        """Return the parser object, creating a new one if needed."""
+        if not self._parser:
+            self._parser = self.createParser()
+            self._intern_setdefault = self._parser.intern.setdefault
+            self._parser.buffer_text = True
+            self._parser.ordered_attributes = True
+            self._parser.specified_attributes = True
+            self.install(self._parser)
+        return self._parser
+
+    def reset(self):
+        """Free all data structures used during DOM construction."""
+        self.document = theDOMImplementation.createDocument(
+            EMPTY_NAMESPACE, None, None)
+        self.curNode = self.document
+        self._elem_info = self.document._elem_info
+        self._cdata = False
+
+    def install(self, parser):
+        """Install the callbacks needed to build the DOM into the parser."""
+        # This creates circular references!
+        parser.StartDoctypeDeclHandler = self.start_doctype_decl_handler
+        parser.StartElementHandler = self.first_element_handler
+        parser.EndElementHandler = self.end_element_handler
+        parser.ProcessingInstructionHandler = self.pi_handler
+        if self._options.entities:
+            parser.EntityDeclHandler = self.entity_decl_handler
+        parser.NotationDeclHandler = self.notation_decl_handler
+        if self._options.comments:
+            parser.CommentHandler = self.comment_handler
+        if self._options.cdata_sections:
+            parser.StartCdataSectionHandler = self.start_cdata_section_handler
+            parser.EndCdataSectionHandler = self.end_cdata_section_handler
+            parser.CharacterDataHandler = self.character_data_handler_cdata
+        else:
+            parser.CharacterDataHandler = self.character_data_handler
+        parser.ExternalEntityRefHandler = self.external_entity_ref_handler
+        parser.XmlDeclHandler = self.xml_decl_handler
+        parser.ElementDeclHandler = self.element_decl_handler
+        parser.AttlistDeclHandler = self.attlist_decl_handler
+
+    def parseFile(self, file):
+        """Parse a document from a file object, returning the document
+        node."""
+        parser = self.getParser()
+        first_buffer = True
+        try:
+            while 1:
+                buffer = file.read(16*1024)
+                if not buffer:
+                    break
+                parser.Parse(buffer, 0)
+                if first_buffer and self.document.documentElement:
+                    self._setup_subset(buffer)
+                first_buffer = False
+            parser.Parse("", True)
+        except ParseEscape:
+            pass
+        doc = self.document
+        self.reset()
+        self._parser = None
+        return doc
+
+    def parseString(self, string):
+        """Parse a document from a string, returning the document node."""
+        parser = self.getParser()
+        try:
+            parser.Parse(string, True)
+            self._setup_subset(string)
+        except ParseEscape:
+            pass
+        doc = self.document
+        self.reset()
+        self._parser = None
+        return doc
+
+    def _setup_subset(self, buffer):
+        """Load the internal subset if there might be one."""
+        if self.document.doctype:
+            extractor = InternalSubsetExtractor()
+            extractor.parseString(buffer)
+            subset = extractor.getSubset()
+            self.document.doctype.internalSubset = subset
+
+    def start_doctype_decl_handler(self, doctypeName, systemId, publicId,
+                                   has_internal_subset):
+        doctype = self.document.implementation.createDocumentType(
+            doctypeName, publicId, systemId)
+        doctype.ownerDocument = self.document
+        _append_child(self.document, doctype)
+        self.document.doctype = doctype
+        if self._filter and self._filter.acceptNode(doctype) == FILTER_REJECT:
+            self.document.doctype = None
+            del self.document.childNodes[-1]
+            doctype = None
+            self._parser.EntityDeclHandler = None
+            self._parser.NotationDeclHandler = None
+        if has_internal_subset:
+            if doctype is not None:
+                doctype.entities._seq = []
+                doctype.notations._seq = []
+            self._parser.CommentHandler = None
+            self._parser.ProcessingInstructionHandler = None
+            self._parser.EndDoctypeDeclHandler = self.end_doctype_decl_handler
+
+    def end_doctype_decl_handler(self):
+        if self._options.comments:
+            self._parser.CommentHandler = self.comment_handler
+        self._parser.ProcessingInstructionHandler = self.pi_handler
+        if not (self._elem_info or self._filter):
+            self._finish_end_element = id
+
+    def pi_handler(self, target, data):
+        node = self.document.createProcessingInstruction(target, data)
+        _append_child(self.curNode, node)
+        if self._filter and self._filter.acceptNode(node) == FILTER_REJECT:
+            self.curNode.removeChild(node)
+
+    def character_data_handler_cdata(self, data):
+        childNodes = self.curNode.childNodes
+        if self._cdata:
+            if (  self._cdata_continue
+                  and childNodes[-1].nodeType == CDATA_SECTION_NODE):
+                childNodes[-1].appendData(data)
+                return
+            node = self.document.createCDATASection(data)
+            self._cdata_continue = True
+        elif childNodes and childNodes[-1].nodeType == TEXT_NODE:
+            node = childNodes[-1]
+            value = node.data + data
+            node.data = value
+            return
+        else:
+            node = minidom.Text()
+            node.data = data
+            node.ownerDocument = self.document
+        _append_child(self.curNode, node)
+
+    def character_data_handler(self, data):
+        childNodes = self.curNode.childNodes
+        if childNodes and childNodes[-1].nodeType == TEXT_NODE:
+            node = childNodes[-1]
+            node.data = node.data + data
+            return
+        node = minidom.Text()
+        node.data = node.data + data
+        node.ownerDocument = self.document
+        _append_child(self.curNode, node)
+
+    def entity_decl_handler(self, entityName, is_parameter_entity, value,
+                            base, systemId, publicId, notationName):
+        if is_parameter_entity:
+            # we don't care about parameter entities for the DOM
+            return
+        if not self._options.entities:
+            return
+        node = self.document._create_entity(entityName, publicId,
+                                            systemId, notationName)
+        if value is not None:
+            # internal entity
+            # node *should* be readonly, but we'll cheat
+            child = self.document.createTextNode(value)
+            node.childNodes.append(child)
+        self.document.doctype.entities._seq.append(node)
+        if self._filter and self._filter.acceptNode(node) == FILTER_REJECT:
+            del self.document.doctype.entities._seq[-1]
+
+    def notation_decl_handler(self, notationName, base, systemId, publicId):
+        node = self.document._create_notation(notationName, publicId, systemId)
+        self.document.doctype.notations._seq.append(node)
+        if self._filter and self._filter.acceptNode(node) == FILTER_ACCEPT:
+            del self.document.doctype.notations._seq[-1]
+
+    def comment_handler(self, data):
+        node = self.document.createComment(data)
+        _append_child(self.curNode, node)
+        if self._filter and self._filter.acceptNode(node) == FILTER_REJECT:
+            self.curNode.removeChild(node)
+
+    def start_cdata_section_handler(self):
+        self._cdata = True
+        self._cdata_continue = False
+
+    def end_cdata_section_handler(self):
+        self._cdata = False
+        self._cdata_continue = False
+
+    def external_entity_ref_handler(self, context, base, systemId, publicId):
+        return 1
+
+    def first_element_handler(self, name, attributes):
+        if self._filter is None and not self._elem_info:
+            self._finish_end_element = id
+        self.getParser().StartElementHandler = self.start_element_handler
+        self.start_element_handler(name, attributes)
+
+    def start_element_handler(self, name, attributes):
+        node = self.document.createElement(name)
+        _append_child(self.curNode, node)
+        self.curNode = node
+
+        if attributes:
+            for i in range(0, len(attributes), 2):
+                a = minidom.Attr(attributes[i], EMPTY_NAMESPACE,
+                                 None, EMPTY_PREFIX)
+                value = attributes[i+1]
+                a.value = value
+                a.ownerDocument = self.document
+                _set_attribute_node(node, a)
+
+        if node is not self.document.documentElement:
+            self._finish_start_element(node)
+
+    def _finish_start_element(self, node):
+        if self._filter:
+            # To be general, we'd have to call isSameNode(), but this
+            # is sufficient for minidom:
+            if node is self.document.documentElement:
+                return
+            filt = self._filter.startContainer(node)
+            if filt == FILTER_REJECT:
+                # ignore this node & all descendents
+                Rejecter(self)
+            elif filt == FILTER_SKIP:
+                # ignore this node, but make it's children become
+                # children of the parent node
+                Skipper(self)
+            else:
+                return
+            self.curNode = node.parentNode
+            node.parentNode.removeChild(node)
+            node.unlink()
+
+    # If this ever changes, Namespaces.end_element_handler() needs to
+    # be changed to match.
+    #
+    def end_element_handler(self, name):
+        curNode = self.curNode
+        self.curNode = curNode.parentNode
+        self._finish_end_element(curNode)
+
+    def _finish_end_element(self, curNode):
+        info = self._elem_info.get(curNode.tagName)
+        if info:
+            self._handle_white_text_nodes(curNode, info)
+        if self._filter:
+            if curNode is self.document.documentElement:
+                return
+            if self._filter.acceptNode(curNode) == FILTER_REJECT:
+                self.curNode.removeChild(curNode)
+                curNode.unlink()
+
+    def _handle_white_text_nodes(self, node, info):
+        if (self._options.whitespace_in_element_content
+            or not info.isElementContent()):
+            return
+
+        # We have element type information and should remove ignorable
+        # whitespace; identify for text nodes which contain only
+        # whitespace.
+        L = []
+        for child in node.childNodes:
+            if child.nodeType == TEXT_NODE and not child.data.strip():
+                L.append(child)
+
+        # Remove ignorable whitespace from the tree.
+        for child in L:
+            node.removeChild(child)
+
+    def element_decl_handler(self, name, model):
+        info = self._elem_info.get(name)
+        if info is None:
+            self._elem_info[name] = ElementInfo(name, model)
+        else:
+            assert info._model is None
+            info._model = model
+
+    def attlist_decl_handler(self, elem, name, type, default, required):
+        info = self._elem_info.get(elem)
+        if info is None:
+            info = ElementInfo(elem)
+            self._elem_info[elem] = info
+        info._attr_info.append(
+            [None, name, None, None, default, 0, type, required])
+
+    def xml_decl_handler(self, version, encoding, standalone):
+        self.document.version = version
+        self.document.encoding = encoding
+        # This is still a little ugly, thanks to the pyexpat API. ;-(
+        if standalone >= 0:
+            if standalone:
+                self.document.standalone = True
+            else:
+                self.document.standalone = False
+
+
+# Don't include FILTER_INTERRUPT, since that's checked separately
+# where allowed.
+_ALLOWED_FILTER_RETURNS = (FILTER_ACCEPT, FILTER_REJECT, FILTER_SKIP)
+
+class FilterVisibilityController(object):
+    """Wrapper around a DOMBuilderFilter which implements the checks
+    to make the whatToShow filter attribute work."""
+
+    __slots__ = 'filter',
+
+    def __init__(self, filter):
+        self.filter = filter
+
+    def startContainer(self, node):
+        mask = self._nodetype_mask[node.nodeType]
+        if self.filter.whatToShow & mask:
+            val = self.filter.startContainer(node)
+            if val == FILTER_INTERRUPT:
+                raise ParseEscape
+            if val not in _ALLOWED_FILTER_RETURNS:
+                raise ValueError(
+                      "startContainer() returned illegal value: " + repr(val))
+            return val
+        else:
+            return FILTER_ACCEPT
+
+    def acceptNode(self, node):
+        mask = self._nodetype_mask[node.nodeType]
+        if self.filter.whatToShow & mask:
+            val = self.filter.acceptNode(node)
+            if val == FILTER_INTERRUPT:
+                raise ParseEscape
+            if val == FILTER_SKIP:
+                # move all child nodes to the parent, and remove this node
+                parent = node.parentNode
+                for child in node.childNodes[:]:
+                    parent.appendChild(child)
+                # node is handled by the caller
+                return FILTER_REJECT
+            if val not in _ALLOWED_FILTER_RETURNS:
+                raise ValueError(
+                      "acceptNode() returned illegal value: " + repr(val))
+            return val
+        else:
+            return FILTER_ACCEPT
+
+    _nodetype_mask = {
+        Node.ELEMENT_NODE:                NodeFilter.SHOW_ELEMENT,
+        Node.ATTRIBUTE_NODE:              NodeFilter.SHOW_ATTRIBUTE,
+        Node.TEXT_NODE:                   NodeFilter.SHOW_TEXT,
+        Node.CDATA_SECTION_NODE:          NodeFilter.SHOW_CDATA_SECTION,
+        Node.ENTITY_REFERENCE_NODE:       NodeFilter.SHOW_ENTITY_REFERENCE,
+        Node.ENTITY_NODE:                 NodeFilter.SHOW_ENTITY,
+        Node.PROCESSING_INSTRUCTION_NODE: NodeFilter.SHOW_PROCESSING_INSTRUCTION,
+        Node.COMMENT_NODE:                NodeFilter.SHOW_COMMENT,
+        Node.DOCUMENT_NODE:               NodeFilter.SHOW_DOCUMENT,
+        Node.DOCUMENT_TYPE_NODE:          NodeFilter.SHOW_DOCUMENT_TYPE,
+        Node.DOCUMENT_FRAGMENT_NODE:      NodeFilter.SHOW_DOCUMENT_FRAGMENT,
+        Node.NOTATION_NODE:               NodeFilter.SHOW_NOTATION,
+        }
+
+
+class FilterCrutch(object):
+    __slots__ = '_builder', '_level', '_old_start', '_old_end'
+
+    def __init__(self, builder):
+        self._level = 0
+        self._builder = builder
+        parser = builder._parser
+        self._old_start = parser.StartElementHandler
+        self._old_end = parser.EndElementHandler
+        parser.StartElementHandler = self.start_element_handler
+        parser.EndElementHandler = self.end_element_handler
+
+class Rejecter(FilterCrutch):
+    __slots__ = ()
+
+    def __init__(self, builder):
+        FilterCrutch.__init__(self, builder)
+        parser = builder._parser
+        for name in ("ProcessingInstructionHandler",
+                     "CommentHandler",
+                     "CharacterDataHandler",
+                     "StartCdataSectionHandler",
+                     "EndCdataSectionHandler",
+                     "ExternalEntityRefHandler",
+                     ):
+            setattr(parser, name, None)
+
+    def start_element_handler(self, *args):
+        self._level = self._level + 1
+
+    def end_element_handler(self, *args):
+        if self._level == 0:
+            # restore the old handlers
+            parser = self._builder._parser
+            self._builder.install(parser)
+            parser.StartElementHandler = self._old_start
+            parser.EndElementHandler = self._old_end
+        else:
+            self._level = self._level - 1
+
+class Skipper(FilterCrutch):
+    __slots__ = ()
+
+    def start_element_handler(self, *args):
+        node = self._builder.curNode
+        self._old_start(*args)
+        if self._builder.curNode is not node:
+            self._level = self._level + 1
+
+    def end_element_handler(self, *args):
+        if self._level == 0:
+            # We're popping back out of the node we're skipping, so we
+            # shouldn't need to do anything but reset the handlers.
+            self._builder._parser.StartElementHandler = self._old_start
+            self._builder._parser.EndElementHandler = self._old_end
+            self._builder = None
+        else:
+            self._level = self._level - 1
+            self._old_end(*args)
+
+
+# framework document used by the fragment builder.
+# Takes a string for the doctype, subset string, and namespace attrs string.
+
+_FRAGMENT_BUILDER_INTERNAL_SYSTEM_ID = \
+    "http://xml.python.org/entities/fragment-builder/internal"
+
+_FRAGMENT_BUILDER_TEMPLATE = (
+    '''\
+<!DOCTYPE wrapper
+  %%s [
+  <!ENTITY fragment-builder-internal
+    SYSTEM "%s">
+%%s
+]>
+<wrapper %%s
+>&fragment-builder-internal;</wrapper>'''
+    % _FRAGMENT_BUILDER_INTERNAL_SYSTEM_ID)
+
+
+class FragmentBuilder(ExpatBuilder):
+    """Builder which constructs document fragments given XML source
+    text and a context node.
+
+    The context node is expected to provide information about the
+    namespace declarations which are in scope at the start of the
+    fragment.
+    """
+
+    def __init__(self, context, options=None):
+        if context.nodeType == DOCUMENT_NODE:
+            self.originalDocument = context
+            self.context = context
+        else:
+            self.originalDocument = context.ownerDocument
+            self.context = context
+        ExpatBuilder.__init__(self, options)
+
+    def reset(self):
+        ExpatBuilder.reset(self)
+        self.fragment = None
+
+    def parseFile(self, file):
+        """Parse a document fragment from a file object, returning the
+        fragment node."""
+        return self.parseString(file.read())
+
+    def parseString(self, string):
+        """Parse a document fragment from a string, returning the
+        fragment node."""
+        self._source = string
+        parser = self.getParser()
+        doctype = self.originalDocument.doctype
+        ident = ""
+        if doctype:
+            subset = doctype.internalSubset or self._getDeclarations()
+            if doctype.publicId:
+                ident = ('PUBLIC "%s" "%s"'
+                         % (doctype.publicId, doctype.systemId))
+            elif doctype.systemId:
+                ident = 'SYSTEM "%s"' % doctype.systemId
+        else:
+            subset = ""
+        nsattrs = self._getNSattrs() # get ns decls from node's ancestors
+        document = _FRAGMENT_BUILDER_TEMPLATE % (ident, subset, nsattrs)
+        try:
+            parser.Parse(document, 1)
+        except:
+            self.reset()
+            raise
+        fragment = self.fragment
+        self.reset()
+##         self._parser = None
+        return fragment
+
+    def _getDeclarations(self):
+        """Re-create the internal subset from the DocumentType node.
+
+        This is only needed if we don't already have the
+        internalSubset as a string.
+        """
+        doctype = self.context.ownerDocument.doctype
+        s = ""
+        if doctype:
+            for i in range(doctype.notations.length):
+                notation = doctype.notations.item(i)
+                if s:
+                    s = s + "\n  "
+                s = "%s<!NOTATION %s" % (s, notation.nodeName)
+                if notation.publicId:
+                    s = '%s PUBLIC "%s"\n             "%s">' \
+                        % (s, notation.publicId, notation.systemId)
+                else:
+                    s = '%s SYSTEM "%s">' % (s, notation.systemId)
+            for i in range(doctype.entities.length):
+                entity = doctype.entities.item(i)
+                if s:
+                    s = s + "\n  "
+                s = "%s<!ENTITY %s" % (s, entity.nodeName)
+                if entity.publicId:
+                    s = '%s PUBLIC "%s"\n             "%s"' \
+                        % (s, entity.publicId, entity.systemId)
+                elif entity.systemId:
+                    s = '%s SYSTEM "%s"' % (s, entity.systemId)
+                else:
+                    s = '%s "%s"' % (s, entity.firstChild.data)
+                if entity.notationName:
+                    s = "%s NOTATION %s" % (s, entity.notationName)
+                s = s + ">"
+        return s
+
+    def _getNSattrs(self):
+        return ""
+
+    def external_entity_ref_handler(self, context, base, systemId, publicId):
+        if systemId == _FRAGMENT_BUILDER_INTERNAL_SYSTEM_ID:
+            # this entref is the one that we made to put the subtree
+            # in; all of our given input is parsed in here.
+            old_document = self.document
+            old_cur_node = self.curNode
+            parser = self._parser.ExternalEntityParserCreate(context)
+            # put the real document back, parse into the fragment to return
+            self.document = self.originalDocument
+            self.fragment = self.document.createDocumentFragment()
+            self.curNode = self.fragment
+            try:
+                parser.Parse(self._source, 1)
+            finally:
+                self.curNode = old_cur_node
+                self.document = old_document
+                self._source = None
+            return -1
+        else:
+            return ExpatBuilder.external_entity_ref_handler(
+                self, context, base, systemId, publicId)
+
+
+class Namespaces:
+    """Mix-in class for builders; adds support for namespaces."""
+
+    def _initNamespaces(self):
+        # list of (prefix, uri) ns declarations.  Namespace attrs are
+        # constructed from this and added to the element's attrs.
+        self._ns_ordered_prefixes = []
+
+    def createParser(self):
+        """Create a new namespace-handling parser."""
+        parser = expat.ParserCreate(namespace_separator=" ")
+        parser.namespace_prefixes = True
+        return parser
+
+    def install(self, parser):
+        """Insert the namespace-handlers onto the parser."""
+        ExpatBuilder.install(self, parser)
+        if self._options.namespace_declarations:
+            parser.StartNamespaceDeclHandler = (
+                self.start_namespace_decl_handler)
+
+    def start_namespace_decl_handler(self, prefix, uri):
+        """Push this namespace declaration on our storage."""
+        self._ns_ordered_prefixes.append((prefix, uri))
+
+    def start_element_handler(self, name, attributes):
+        if ' ' in name:
+            uri, localname, prefix, qname = _parse_ns_name(self, name)
+        else:
+            uri = EMPTY_NAMESPACE
+            qname = name
+            localname = None
+            prefix = EMPTY_PREFIX
+        node = minidom.Element(qname, uri, prefix, localname)
+        node.ownerDocument = self.document
+        _append_child(self.curNode, node)
+        self.curNode = node
+
+        if self._ns_ordered_prefixes:
+            for prefix, uri in self._ns_ordered_prefixes:
+                if prefix:
+                    a = minidom.Attr(_intern(self, 'xmlns:' + prefix),
+                                     XMLNS_NAMESPACE, prefix, "xmlns")
+                else:
+                    a = minidom.Attr("xmlns", XMLNS_NAMESPACE,
+                                     "xmlns", EMPTY_PREFIX)
+                a.value = uri
+                a.ownerDocument = self.document
+                _set_attribute_node(node, a)
+            del self._ns_ordered_prefixes[:]
+
+        if attributes:
+            node._ensure_attributes()
+            _attrs = node._attrs
+            _attrsNS = node._attrsNS
+            for i in range(0, len(attributes), 2):
+                aname = attributes[i]
+                value = attributes[i+1]
+                if ' ' in aname:
+                    uri, localname, prefix, qname = _parse_ns_name(self, aname)
+                    a = minidom.Attr(qname, uri, localname, prefix)
+                    _attrs[qname] = a
+                    _attrsNS[(uri, localname)] = a
+                else:
+                    a = minidom.Attr(aname, EMPTY_NAMESPACE,
+                                     aname, EMPTY_PREFIX)
+                    _attrs[aname] = a
+                    _attrsNS[(EMPTY_NAMESPACE, aname)] = a
+                a.ownerDocument = self.document
+                a.value = value
+                a.ownerElement = node
+
+    if __debug__:
+        # This only adds some asserts to the original
+        # end_element_handler(), so we only define this when -O is not
+        # used.  If changing one, be sure to check the other to see if
+        # it needs to be changed as well.
+        #
+        def end_element_handler(self, name):
+            curNode = self.curNode
+            if ' ' in name:
+                uri, localname, prefix, qname = _parse_ns_name(self, name)
+                assert (curNode.namespaceURI == uri
+                        and curNode.localName == localname
+                        and curNode.prefix == prefix), \
+                        "element stack messed up! (namespace)"
+            else:
+                assert curNode.nodeName == name, \
+                       "element stack messed up - bad nodeName"
+                assert curNode.namespaceURI == EMPTY_NAMESPACE, \
+                       "element stack messed up - bad namespaceURI"
+            self.curNode = curNode.parentNode
+            self._finish_end_element(curNode)
+
+
+class ExpatBuilderNS(Namespaces, ExpatBuilder):
+    """Document builder that supports namespaces."""
+
+    def reset(self):
+        ExpatBuilder.reset(self)
+        self._initNamespaces()
+
+
+class FragmentBuilderNS(Namespaces, FragmentBuilder):
+    """Fragment builder that supports namespaces."""
+
+    def reset(self):
+        FragmentBuilder.reset(self)
+        self._initNamespaces()
+
+    def _getNSattrs(self):
+        """Return string of namespace attributes from this element and
+        ancestors."""
+        # XXX This needs to be re-written to walk the ancestors of the
+        # context to build up the namespace information from
+        # declarations, elements, and attributes found in context.
+        # Otherwise we have to store a bunch more data on the DOM
+        # (though that *might* be more reliable -- not clear).
+        attrs = ""
+        context = self.context
+        L = []
+        while context:
+            if hasattr(context, '_ns_prefix_uri'):
+                for prefix, uri in context._ns_prefix_uri.items():
+                    # add every new NS decl from context to L and attrs string
+                    if prefix in L:
+                        continue
+                    L.append(prefix)
+                    if prefix:
+                        declname = "xmlns:" + prefix
+                    else:
+                        declname = "xmlns"
+                    if attrs:
+                        attrs = "%s\n    %s='%s'" % (attrs, declname, uri)
+                    else:
+                        attrs = " %s='%s'" % (declname, uri)
+            context = context.parentNode
+        return attrs
+
+
+class ParseEscape(Exception):
+    """Exception raised to short-circuit parsing in InternalSubsetExtractor."""
+    pass
+
+class InternalSubsetExtractor(ExpatBuilder):
+    """XML processor which can rip out the internal document type subset."""
+
+    subset = None
+
+    def getSubset(self):
+        """Return the internal subset as a string."""
+        return self.subset
+
+    def parseFile(self, file):
+        try:
+            ExpatBuilder.parseFile(self, file)
+        except ParseEscape:
+            pass
+
+    def parseString(self, string):
+        try:
+            ExpatBuilder.parseString(self, string)
+        except ParseEscape:
+            pass
+
+    def install(self, parser):
+        parser.StartDoctypeDeclHandler = self.start_doctype_decl_handler
+        parser.StartElementHandler = self.start_element_handler
+
+    def start_doctype_decl_handler(self, name, publicId, systemId,
+                                   has_internal_subset):
+        if has_internal_subset:
+            parser = self.getParser()
+            self.subset = []
+            parser.DefaultHandler = self.subset.append
+            parser.EndDoctypeDeclHandler = self.end_doctype_decl_handler
+        else:
+            raise ParseEscape()
+
+    def end_doctype_decl_handler(self):
+        s = ''.join(self.subset).replace('\r\n', '\n').replace('\r', '\n')
+        self.subset = s
+        raise ParseEscape()
+
+    def start_element_handler(self, name, attrs):
+        raise ParseEscape()
+
+
+def parse(file, namespaces=True):
+    """Parse a document, returning the resulting Document node.
+
+    'file' may be either a file name or an open file object.
+    """
+    if namespaces:
+        builder = ExpatBuilderNS()
+    else:
+        builder = ExpatBuilder()
+
+    if isinstance(file, str):
+        with open(file, 'rb') as fp:
+            result = builder.parseFile(fp)
+    else:
+        result = builder.parseFile(file)
+    return result
+
+
+def parseString(string, namespaces=True):
+    """Parse a document from a string, returning the resulting
+    Document node.
+    """
+    if namespaces:
+        builder = ExpatBuilderNS()
+    else:
+        builder = ExpatBuilder()
+    return builder.parseString(string)
+
+
+def parseFragment(file, context, namespaces=True):
+    """Parse a fragment of a document, given the context from which it
+    was originally extracted.  context should be the parent of the
+    node(s) which are in the fragment.
+
+    'file' may be either a file name or an open file object.
+    """
+    if namespaces:
+        builder = FragmentBuilderNS(context)
+    else:
+        builder = FragmentBuilder(context)
+
+    if isinstance(file, str):
+        with open(file, 'rb') as fp:
+            result = builder.parseFile(fp)
+    else:
+        result = builder.parseFile(file)
+    return result
+
+
+def parseFragmentString(string, context, namespaces=True):
+    """Parse a fragment of a document from a string, given the context
+    from which it was originally extracted.  context should be the
+    parent of the node(s) which are in the fragment.
+    """
+    if namespaces:
+        builder = FragmentBuilderNS(context)
+    else:
+        builder = FragmentBuilder(context)
+    return builder.parseString(string)
+
+
+def makeBuilder(options):
+    """Create a builder based on an Options object."""
+    if options.namespaces:
+        return ExpatBuilderNS(options)
+    else:
+        return ExpatBuilder(options)
diff --git a/Lib/xml/dom/minicompat.py b/Lib/xml/dom/minicompat.py
new file mode 100644
index 000000000..5d6fae9a2
--- /dev/null
+++ b/Lib/xml/dom/minicompat.py
@@ -0,0 +1,109 @@
+"""Python version compatibility support for minidom.
+
+This module contains internal implementation details and
+should not be imported; use xml.dom.minidom instead.
+"""
+
+# This module should only be imported using "import *".
+#
+# The following names are defined:
+#
+#   NodeList      -- lightest possible NodeList implementation
+#
+#   EmptyNodeList -- lightest possible NodeList that is guaranteed to
+#                    remain empty (immutable)
+#
+#   StringTypes   -- tuple of defined string types
+#
+#   defproperty   -- function used in conjunction with GetattrMagic;
+#                    using these together is needed to make them work
+#                    as efficiently as possible in both Python 2.2+
+#                    and older versions.  For example:
+#
+#                        class MyClass(GetattrMagic):
+#                            def _get_myattr(self):
+#                                return something
+#
+#                        defproperty(MyClass, "myattr",
+#                                    "return some value")
+#
+#                    For Python 2.2 and newer, this will construct a
+#                    property object on the class, which avoids
+#                    needing to override __getattr__().  It will only
+#                    work for read-only attributes.
+#
+#                    For older versions of Python, inheriting from
+#                    GetattrMagic will use the traditional
+#                    __getattr__() hackery to achieve the same effect,
+#                    but less efficiently.
+#
+#                    defproperty() should be used for each version of
+#                    the relevant _get_<property>() function.
+
+__all__ = ["NodeList", "EmptyNodeList", "StringTypes", "defproperty"]
+
+import xml.dom
+
+StringTypes = (str,)
+
+
+class NodeList(list):
+    __slots__ = ()
+
+    def item(self, index):
+        if 0 <= index < len(self):
+            return self[index]
+
+    def _get_length(self):
+        return len(self)
+
+    def _set_length(self, value):
+        raise xml.dom.NoModificationAllowedErr(
+            "attempt to modify read-only attribute 'length'")
+
+    length = property(_get_length, _set_length,
+                      doc="The number of nodes in the NodeList.")
+
+    # For backward compatibility
+    def __setstate__(self, state):
+        if state is None:
+            state = []
+        self[:] = state
+
+
+class EmptyNodeList(tuple):
+    __slots__ = ()
+
+    def __add__(self, other):
+        NL = NodeList()
+        NL.extend(other)
+        return NL
+
+    def __radd__(self, other):
+        NL = NodeList()
+        NL.extend(other)
+        return NL
+
+    def item(self, index):
+        return None
+
+    def _get_length(self):
+        return 0
+
+    def _set_length(self, value):
+        raise xml.dom.NoModificationAllowedErr(
+            "attempt to modify read-only attribute 'length'")
+
+    length = property(_get_length, _set_length,
+                      doc="The number of nodes in the NodeList.")
+
+
+def defproperty(klass, name, doc):
+    get = getattr(klass, ("_get_" + name))
+    def set(self, value, name=name):
+        raise xml.dom.NoModificationAllowedErr(
+            "attempt to modify read-only attribute " + repr(name))
+    assert not hasattr(klass, "_set_" + name), \
+           "expected not to find _set_" + name
+    prop = property(get, set, doc=doc)
+    setattr(klass, name, prop)
diff --git a/Lib/xml/dom/minidom.py b/Lib/xml/dom/minidom.py
new file mode 100644
index 000000000..24957ea14
--- /dev/null
+++ b/Lib/xml/dom/minidom.py
@@ -0,0 +1,1981 @@
+"""Simple implementation of the Level 1 DOM.
+
+Namespaces and other minor Level 2 features are also supported.
+
+parse("foo.xml")
+
+parseString("<foo><bar/></foo>")
+
+Todo:
+=====
+ * convenience methods for getting elements and text.
+ * more testing
+ * bring some of the writer and linearizer code into conformance with this
+        interface
+ * SAX 2 namespaces
+"""
+
+import io
+import xml.dom
+
+from xml.dom import EMPTY_NAMESPACE, EMPTY_PREFIX, XMLNS_NAMESPACE, domreg
+from xml.dom.minicompat import *
+from xml.dom.xmlbuilder import DOMImplementationLS, DocumentLS
+
+# This is used by the ID-cache invalidation checks; the list isn't
+# actually complete, since the nodes being checked will never be the
+# DOCUMENT_NODE or DOCUMENT_FRAGMENT_NODE.  (The node being checked is
+# the node being added or removed, not the node being modified.)
+#
+_nodeTypes_with_children = (xml.dom.Node.ELEMENT_NODE,
+                            xml.dom.Node.ENTITY_REFERENCE_NODE)
+
+
+class Node(xml.dom.Node):
+    namespaceURI = None # this is non-null only for elements and attributes
+    parentNode = None
+    ownerDocument = None
+    nextSibling = None
+    previousSibling = None
+
+    prefix = EMPTY_PREFIX # non-null only for NS elements and attributes
+
+    def __bool__(self):
+        return True
+
+    def toxml(self, encoding=None):
+        return self.toprettyxml("", "", encoding)
+
+    def toprettyxml(self, indent="\t", newl="\n", encoding=None):
+        if encoding is None:
+            writer = io.StringIO()
+        else:
+            writer = io.TextIOWrapper(io.BytesIO(),
+                                      encoding=encoding,
+                                      errors="xmlcharrefreplace",
+                                      newline='\n')
+        if self.nodeType == Node.DOCUMENT_NODE:
+            # Can pass encoding only to document, to put it into XML header
+            self.writexml(writer, "", indent, newl, encoding)
+        else:
+            self.writexml(writer, "", indent, newl)
+        if encoding is None:
+            return writer.getvalue()
+        else:
+            return writer.detach().getvalue()
+
+    def hasChildNodes(self):
+        return bool(self.childNodes)
+
+    def _get_childNodes(self):
+        return self.childNodes
+
+    def _get_firstChild(self):
+        if self.childNodes:
+            return self.childNodes[0]
+
+    def _get_lastChild(self):
+        if self.childNodes:
+            return self.childNodes[-1]
+
+    def insertBefore(self, newChild, refChild):
+        if newChild.nodeType == self.DOCUMENT_FRAGMENT_NODE:
+            for c in tuple(newChild.childNodes):
+                self.insertBefore(c, refChild)
+            ### The DOM does not clearly specify what to return in this case
+            return newChild
+        if newChild.nodeType not in self._child_node_types:
+            raise xml.dom.HierarchyRequestErr(
+                "%s cannot be child of %s" % (repr(newChild), repr(self)))
+        if newChild.parentNode is not None:
+            newChild.parentNode.removeChild(newChild)
+        if refChild is None:
+            self.appendChild(newChild)
+        else:
+            try:
+                index = self.childNodes.index(refChild)
+            except ValueError:
+                raise xml.dom.NotFoundErr()
+            if newChild.nodeType in _nodeTypes_with_children:
+                _clear_id_cache(self)
+            self.childNodes.insert(index, newChild)
+            newChild.nextSibling = refChild
+            refChild.previousSibling = newChild
+            if index:
+                node = self.childNodes[index-1]
+                node.nextSibling = newChild
+                newChild.previousSibling = node
+            else:
+                newChild.previousSibling = None
+            newChild.parentNode = self
+        return newChild
+
+    def appendChild(self, node):
+        if node.nodeType == self.DOCUMENT_FRAGMENT_NODE:
+            for c in tuple(node.childNodes):
+                self.appendChild(c)
+            ### The DOM does not clearly specify what to return in this case
+            return node
+        if node.nodeType not in self._child_node_types:
+            raise xml.dom.HierarchyRequestErr(
+                "%s cannot be child of %s" % (repr(node), repr(self)))
+        elif node.nodeType in _nodeTypes_with_children:
+            _clear_id_cache(self)
+        if node.parentNode is not None:
+            node.parentNode.removeChild(node)
+        _append_child(self, node)
+        node.nextSibling = None
+        return node
+
+    def replaceChild(self, newChild, oldChild):
+        if newChild.nodeType == self.DOCUMENT_FRAGMENT_NODE:
+            refChild = oldChild.nextSibling
+            self.removeChild(oldChild)
+            return self.insertBefore(newChild, refChild)
+        if newChild.nodeType not in self._child_node_types:
+            raise xml.dom.HierarchyRequestErr(
+                "%s cannot be child of %s" % (repr(newChild), repr(self)))
+        if newChild is oldChild:
+            return
+        if newChild.parentNode is not None:
+            newChild.parentNode.removeChild(newChild)
+        try:
+            index = self.childNodes.index(oldChild)
+        except ValueError:
+            raise xml.dom.NotFoundErr()
+        self.childNodes[index] = newChild
+        newChild.parentNode = self
+        oldChild.parentNode = None
+        if (newChild.nodeType in _nodeTypes_with_children
+            or oldChild.nodeType in _nodeTypes_with_children):
+            _clear_id_cache(self)
+        newChild.nextSibling = oldChild.nextSibling
+        newChild.previousSibling = oldChild.previousSibling
+        oldChild.nextSibling = None
+        oldChild.previousSibling = None
+        if newChild.previousSibling:
+            newChild.previousSibling.nextSibling = newChild
+        if newChild.nextSibling:
+            newChild.nextSibling.previousSibling = newChild
+        return oldChild
+
+    def removeChild(self, oldChild):
+        try:
+            self.childNodes.remove(oldChild)
+        except ValueError:
+            raise xml.dom.NotFoundErr()
+        if oldChild.nextSibling is not None:
+            oldChild.nextSibling.previousSibling = oldChild.previousSibling
+        if oldChild.previousSibling is not None:
+            oldChild.previousSibling.nextSibling = oldChild.nextSibling
+        oldChild.nextSibling = oldChild.previousSibling = None
+        if oldChild.nodeType in _nodeTypes_with_children:
+            _clear_id_cache(self)
+
+        oldChild.parentNode = None
+        return oldChild
+
+    def normalize(self):
+        L = []
+        for child in self.childNodes:
+            if child.nodeType == Node.TEXT_NODE:
+                if not child.data:
+                    # empty text node; discard
+                    if L:
+                        L[-1].nextSibling = child.nextSibling
+                    if child.nextSibling:
+                        child.nextSibling.previousSibling = child.previousSibling
+                    child.unlink()
+                elif L and L[-1].nodeType == child.nodeType:
+                    # collapse text node
+                    node = L[-1]
+                    node.data = node.data + child.data
+                    node.nextSibling = child.nextSibling
+                    if child.nextSibling:
+                        child.nextSibling.previousSibling = node
+                    child.unlink()
+                else:
+                    L.append(child)
+            else:
+                L.append(child)
+                if child.nodeType == Node.ELEMENT_NODE:
+                    child.normalize()
+        self.childNodes[:] = L
+
+    def cloneNode(self, deep):
+        return _clone_node(self, deep, self.ownerDocument or self)
+
+    def isSupported(self, feature, version):
+        return self.ownerDocument.implementation.hasFeature(feature, version)
+
+    def _get_localName(self):
+        # Overridden in Element and Attr where localName can be Non-Null
+        return None
+
+    # Node interfaces from Level 3 (WD 9 April 2002)
+
+    def isSameNode(self, other):
+        return self is other
+
+    def getInterface(self, feature):
+        if self.isSupported(feature, None):
+            return self
+        else:
+            return None
+
+    # The "user data" functions use a dictionary that is only present
+    # if some user data has been set, so be careful not to assume it
+    # exists.
+
+    def getUserData(self, key):
+        try:
+            return self._user_data[key][0]
+        except (AttributeError, KeyError):
+            return None
+
+    def setUserData(self, key, data, handler):
+        old = None
+        try:
+            d = self._user_data
+        except AttributeError:
+            d = {}
+            self._user_data = d
+        if key in d:
+            old = d[key][0]
+        if data is None:
+            # ignore handlers passed for None
+            handler = None
+            if old is not None:
+                del d[key]
+        else:
+            d[key] = (data, handler)
+        return old
+
+    def _call_user_data_handler(self, operation, src, dst):
+        if hasattr(self, "_user_data"):
+            for key, (data, handler) in list(self._user_data.items()):
+                if handler is not None:
+                    handler.handle(operation, key, data, src, dst)
+
+    # minidom-specific API:
+
+    def unlink(self):
+        self.parentNode = self.ownerDocument = None
+        if self.childNodes:
+            for child in self.childNodes:
+                child.unlink()
+            self.childNodes = NodeList()
+        self.previousSibling = None
+        self.nextSibling = None
+
+    # A Node is its own context manager, to ensure that an unlink() call occurs.
+    # This is similar to how a file object works.
+    def __enter__(self):
+        return self
+
+    def __exit__(self, et, ev, tb):
+        self.unlink()
+
+defproperty(Node, "firstChild", doc="First child node, or None.")
+defproperty(Node, "lastChild",  doc="Last child node, or None.")
+defproperty(Node, "localName",  doc="Namespace-local name of this node.")
+
+
+def _append_child(self, node):
+    # fast path with less checks; usable by DOM builders if careful
+    childNodes = self.childNodes
+    if childNodes:
+        last = childNodes[-1]
+        node.previousSibling = last
+        last.nextSibling = node
+    childNodes.append(node)
+    node.parentNode = self
+
+def _in_document(node):
+    # return True iff node is part of a document tree
+    while node is not None:
+        if node.nodeType == Node.DOCUMENT_NODE:
+            return True
+        node = node.parentNode
+    return False
+
+def _write_data(writer, data):
+    "Writes datachars to writer."
+    if data:
+        data = data.replace("&", "&amp;").replace("<", "&lt;"). \
+                    replace("\"", "&quot;").replace(">", "&gt;")
+        writer.write(data)
+
+def _get_elements_by_tagName_helper(parent, name, rc):
+    for node in parent.childNodes:
+        if node.nodeType == Node.ELEMENT_NODE and \
+            (name == "*" or node.tagName == name):
+            rc.append(node)
+        _get_elements_by_tagName_helper(node, name, rc)
+    return rc
+
+def _get_elements_by_tagName_ns_helper(parent, nsURI, localName, rc):
+    for node in parent.childNodes:
+        if node.nodeType == Node.ELEMENT_NODE:
+            if ((localName == "*" or node.localName == localName) and
+                (nsURI == "*" or node.namespaceURI == nsURI)):
+                rc.append(node)
+            _get_elements_by_tagName_ns_helper(node, nsURI, localName, rc)
+    return rc
+
+class DocumentFragment(Node):
+    nodeType = Node.DOCUMENT_FRAGMENT_NODE
+    nodeName = "#document-fragment"
+    nodeValue = None
+    attributes = None
+    parentNode = None
+    _child_node_types = (Node.ELEMENT_NODE,
+                         Node.TEXT_NODE,
+                         Node.CDATA_SECTION_NODE,
+                         Node.ENTITY_REFERENCE_NODE,
+                         Node.PROCESSING_INSTRUCTION_NODE,
+                         Node.COMMENT_NODE,
+                         Node.NOTATION_NODE)
+
+    def __init__(self):
+        self.childNodes = NodeList()
+
+
+class Attr(Node):
+    __slots__=('_name', '_value', 'namespaceURI',
+               '_prefix', 'childNodes', '_localName', 'ownerDocument', 'ownerElement')
+    nodeType = Node.ATTRIBUTE_NODE
+    attributes = None
+    specified = False
+    _is_id = False
+
+    _child_node_types = (Node.TEXT_NODE, Node.ENTITY_REFERENCE_NODE)
+
+    def __init__(self, qName, namespaceURI=EMPTY_NAMESPACE, localName=None,
+                 prefix=None):
+        self.ownerElement = None
+        self._name = qName
+        self.namespaceURI = namespaceURI
+        self._prefix = prefix
+        self.childNodes = NodeList()
+
+        # Add the single child node that represents the value of the attr
+        self.childNodes.append(Text())
+
+        # nodeValue and value are set elsewhere
+
+    def _get_localName(self):
+        try:
+            return self._localName
+        except AttributeError:
+            return self.nodeName.split(":", 1)[-1]
+
+    def _get_specified(self):
+        return self.specified
+
+    def _get_name(self):
+        return self._name
+
+    def _set_name(self, value):
+        self._name = value
+        if self.ownerElement is not None:
+            _clear_id_cache(self.ownerElement)
+
+    nodeName = name = property(_get_name, _set_name)
+
+    def _get_value(self):
+        return self._value
+
+    def _set_value(self, value):
+        self._value = value
+        self.childNodes[0].data = value
+        if self.ownerElement is not None:
+            _clear_id_cache(self.ownerElement)
+        self.childNodes[0].data = value
+
+    nodeValue = value = property(_get_value, _set_value)
+
+    def _get_prefix(self):
+        return self._prefix
+
+    def _set_prefix(self, prefix):
+        nsuri = self.namespaceURI
+        if prefix == "xmlns":
+            if nsuri and nsuri != XMLNS_NAMESPACE:
+                raise xml.dom.NamespaceErr(
+                    "illegal use of 'xmlns' prefix for the wrong namespace")
+        self._prefix = prefix
+        if prefix is None:
+            newName = self.localName
+        else:
+            newName = "%s:%s" % (prefix, self.localName)
+        if self.ownerElement:
+            _clear_id_cache(self.ownerElement)
+        self.name = newName
+
+    prefix = property(_get_prefix, _set_prefix)
+
+    def unlink(self):
+        # This implementation does not call the base implementation
+        # since most of that is not needed, and the expense of the
+        # method call is not warranted.  We duplicate the removal of
+        # children, but that's all we needed from the base class.
+        elem = self.ownerElement
+        if elem is not None:
+            del elem._attrs[self.nodeName]
+            del elem._attrsNS[(self.namespaceURI, self.localName)]
+            if self._is_id:
+                self._is_id = False
+                elem._magic_id_nodes -= 1
+                self.ownerDocument._magic_id_count -= 1
+        for child in self.childNodes:
+            child.unlink()
+        del self.childNodes[:]
+
+    def _get_isId(self):
+        if self._is_id:
+            return True
+        doc = self.ownerDocument
+        elem = self.ownerElement
+        if doc is None or elem is None:
+            return False
+
+        info = doc._get_elem_info(elem)
+        if info is None:
+            return False
+        if self.namespaceURI:
+            return info.isIdNS(self.namespaceURI, self.localName)
+        else:
+            return info.isId(self.nodeName)
+
+    def _get_schemaType(self):
+        doc = self.ownerDocument
+        elem = self.ownerElement
+        if doc is None or elem is None:
+            return _no_type
+
+        info = doc._get_elem_info(elem)
+        if info is None:
+            return _no_type
+        if self.namespaceURI:
+            return info.getAttributeTypeNS(self.namespaceURI, self.localName)
+        else:
+            return info.getAttributeType(self.nodeName)
+
+defproperty(Attr, "isId",       doc="True if this attribute is an ID.")
+defproperty(Attr, "localName",  doc="Namespace-local name of this attribute.")
+defproperty(Attr, "schemaType", doc="Schema type for this attribute.")
+
+
+class NamedNodeMap(object):
+    """The attribute list is a transient interface to the underlying
+    dictionaries.  Mutations here will change the underlying element's
+    dictionary.
+
+    Ordering is imposed artificially and does not reflect the order of
+    attributes as found in an input document.
+    """
+
+    __slots__ = ('_attrs', '_attrsNS', '_ownerElement')
+
+    def __init__(self, attrs, attrsNS, ownerElement):
+        self._attrs = attrs
+        self._attrsNS = attrsNS
+        self._ownerElement = ownerElement
+
+    def _get_length(self):
+        return len(self._attrs)
+
+    def item(self, index):
+        try:
+            return self[list(self._attrs.keys())[index]]
+        except IndexError:
+            return None
+
+    def items(self):
+        L = []
+        for node in self._attrs.values():
+            L.append((node.nodeName, node.value))
+        return L
+
+    def itemsNS(self):
+        L = []
+        for node in self._attrs.values():
+            L.append(((node.namespaceURI, node.localName), node.value))
+        return L
+
+    def __contains__(self, key):
+        if isinstance(key, str):
+            return key in self._attrs
+        else:
+            return key in self._attrsNS
+
+    def keys(self):
+        return self._attrs.keys()
+
+    def keysNS(self):
+        return self._attrsNS.keys()
+
+    def values(self):
+        return self._attrs.values()
+
+    def get(self, name, value=None):
+        return self._attrs.get(name, value)
+
+    __len__ = _get_length
+
+    def _cmp(self, other):
+        if self._attrs is getattr(other, "_attrs", None):
+            return 0
+        else:
+            return (id(self) > id(other)) - (id(self) < id(other))
+
+    def __eq__(self, other):
+        return self._cmp(other) == 0
+
+    def __ge__(self, other):
+        return self._cmp(other) >= 0
+
+    def __gt__(self, other):
+        return self._cmp(other) > 0
+
+    def __le__(self, other):
+        return self._cmp(other) <= 0
+
+    def __lt__(self, other):
+        return self._cmp(other) < 0
+
+    def __getitem__(self, attname_or_tuple):
+        if isinstance(attname_or_tuple, tuple):
+            return self._attrsNS[attname_or_tuple]
+        else:
+            return self._attrs[attname_or_tuple]
+
+    # same as set
+    def __setitem__(self, attname, value):
+        if isinstance(value, str):
+            try:
+                node = self._attrs[attname]
+            except KeyError:
+                node = Attr(attname)
+                node.ownerDocument = self._ownerElement.ownerDocument
+                self.setNamedItem(node)
+            node.value = value
+        else:
+            if not isinstance(value, Attr):
+                raise TypeError("value must be a string or Attr object")
+            node = value
+            self.setNamedItem(node)
+
+    def getNamedItem(self, name):
+        try:
+            return self._attrs[name]
+        except KeyError:
+            return None
+
+    def getNamedItemNS(self, namespaceURI, localName):
+        try:
+            return self._attrsNS[(namespaceURI, localName)]
+        except KeyError:
+            return None
+
+    def removeNamedItem(self, name):
+        n = self.getNamedItem(name)
+        if n is not None:
+            _clear_id_cache(self._ownerElement)
+            del self._attrs[n.nodeName]
+            del self._attrsNS[(n.namespaceURI, n.localName)]
+            if hasattr(n, 'ownerElement'):
+                n.ownerElement = None
+            return n
+        else:
+            raise xml.dom.NotFoundErr()
+
+    def removeNamedItemNS(self, namespaceURI, localName):
+        n = self.getNamedItemNS(namespaceURI, localName)
+        if n is not None:
+            _clear_id_cache(self._ownerElement)
+            del self._attrsNS[(n.namespaceURI, n.localName)]
+            del self._attrs[n.nodeName]
+            if hasattr(n, 'ownerElement'):
+                n.ownerElement = None
+            return n
+        else:
+            raise xml.dom.NotFoundErr()
+
+    def setNamedItem(self, node):
+        if not isinstance(node, Attr):
+            raise xml.dom.HierarchyRequestErr(
+                "%s cannot be child of %s" % (repr(node), repr(self)))
+        old = self._attrs.get(node.name)
+        if old:
+            old.unlink()
+        self._attrs[node.name] = node
+        self._attrsNS[(node.namespaceURI, node.localName)] = node
+        node.ownerElement = self._ownerElement
+        _clear_id_cache(node.ownerElement)
+        return old
+
+    def setNamedItemNS(self, node):
+        return self.setNamedItem(node)
+
+    def __delitem__(self, attname_or_tuple):
+        node = self[attname_or_tuple]
+        _clear_id_cache(node.ownerElement)
+        node.unlink()
+
+    def __getstate__(self):
+        return self._attrs, self._attrsNS, self._ownerElement
+
+    def __setstate__(self, state):
+        self._attrs, self._attrsNS, self._ownerElement = state
+
+defproperty(NamedNodeMap, "length",
+            doc="Number of nodes in the NamedNodeMap.")
+
+AttributeList = NamedNodeMap
+
+
+class TypeInfo(object):
+    __slots__ = 'namespace', 'name'
+
+    def __init__(self, namespace, name):
+        self.namespace = namespace
+        self.name = name
+
+    def __repr__(self):
+        if self.namespace:
+            return "<%s %r (from %r)>" % (self.__class__.__name__, self.name,
+                                          self.namespace)
+        else:
+            return "<%s %r>" % (self.__class__.__name__, self.name)
+
+    def _get_name(self):
+        return self.name
+
+    def _get_namespace(self):
+        return self.namespace
+
+_no_type = TypeInfo(None, None)
+
+class Element(Node):
+    __slots__=('ownerDocument', 'parentNode', 'tagName', 'nodeName', 'prefix',
+               'namespaceURI', '_localName', 'childNodes', '_attrs', '_attrsNS',
+               'nextSibling', 'previousSibling')
+    nodeType = Node.ELEMENT_NODE
+    nodeValue = None
+    schemaType = _no_type
+
+    _magic_id_nodes = 0
+
+    _child_node_types = (Node.ELEMENT_NODE,
+                         Node.PROCESSING_INSTRUCTION_NODE,
+                         Node.COMMENT_NODE,
+                         Node.TEXT_NODE,
+                         Node.CDATA_SECTION_NODE,
+                         Node.ENTITY_REFERENCE_NODE)
+
+    def __init__(self, tagName, namespaceURI=EMPTY_NAMESPACE, prefix=None,
+                 localName=None):
+        self.parentNode = None
+        self.tagName = self.nodeName = tagName
+        self.prefix = prefix
+        self.namespaceURI = namespaceURI
+        self.childNodes = NodeList()
+        self.nextSibling = self.previousSibling = None
+
+        # Attribute dictionaries are lazily created
+        # attributes are double-indexed:
+        #    tagName -> Attribute
+        #    URI,localName -> Attribute
+        # in the future: consider lazy generation
+        # of attribute objects this is too tricky
+        # for now because of headaches with
+        # namespaces.
+        self._attrs = None
+        self._attrsNS = None
+
+    def _ensure_attributes(self):
+        if self._attrs is None:
+            self._attrs = {}
+            self._attrsNS = {}
+
+    def _get_localName(self):
+        try:
+            return self._localName
+        except AttributeError:
+            return self.tagName.split(":", 1)[-1]
+
+    def _get_tagName(self):
+        return self.tagName
+
+    def unlink(self):
+        if self._attrs is not None:
+            for attr in list(self._attrs.values()):
+                attr.unlink()
+        self._attrs = None
+        self._attrsNS = None
+        Node.unlink(self)
+
+    def getAttribute(self, attname):
+        if self._attrs is None:
+            return ""
+        try:
+            return self._attrs[attname].value
+        except KeyError:
+            return ""
+
+    def getAttributeNS(self, namespaceURI, localName):
+        if self._attrsNS is None:
+            return ""
+        try:
+            return self._attrsNS[(namespaceURI, localName)].value
+        except KeyError:
+            return ""
+
+    def setAttribute(self, attname, value):
+        attr = self.getAttributeNode(attname)
+        if attr is None:
+            attr = Attr(attname)
+            attr.value = value # also sets nodeValue
+            attr.ownerDocument = self.ownerDocument
+            self.setAttributeNode(attr)
+        elif value != attr.value:
+            attr.value = value
+            if attr.isId:
+                _clear_id_cache(self)
+
+    def setAttributeNS(self, namespaceURI, qualifiedName, value):
+        prefix, localname = _nssplit(qualifiedName)
+        attr = self.getAttributeNodeNS(namespaceURI, localname)
+        if attr is None:
+            attr = Attr(qualifiedName, namespaceURI, localname, prefix)
+            attr.value = value
+            attr.ownerDocument = self.ownerDocument
+            self.setAttributeNode(attr)
+        else:
+            if value != attr.value:
+                attr.value = value
+                if attr.isId:
+                    _clear_id_cache(self)
+            if attr.prefix != prefix:
+                attr.prefix = prefix
+                attr.nodeName = qualifiedName
+
+    def getAttributeNode(self, attrname):
+        if self._attrs is None:
+            return None
+        return self._attrs.get(attrname)
+
+    def getAttributeNodeNS(self, namespaceURI, localName):
+        if self._attrsNS is None:
+            return None
+        return self._attrsNS.get((namespaceURI, localName))
+
+    def setAttributeNode(self, attr):
+        if attr.ownerElement not in (None, self):
+            raise xml.dom.InuseAttributeErr("attribute node already owned")
+        self._ensure_attributes()
+        old1 = self._attrs.get(attr.name, None)
+        if old1 is not None:
+            self.removeAttributeNode(old1)
+        old2 = self._attrsNS.get((attr.namespaceURI, attr.localName), None)
+        if old2 is not None and old2 is not old1:
+            self.removeAttributeNode(old2)
+        _set_attribute_node(self, attr)
+
+        if old1 is not attr:
+            # It might have already been part of this node, in which case
+            # it doesn't represent a change, and should not be returned.
+            return old1
+        if old2 is not attr:
+            return old2
+
+    setAttributeNodeNS = setAttributeNode
+
+    def removeAttribute(self, name):
+        if self._attrsNS is None:
+            raise xml.dom.NotFoundErr()
+        try:
+            attr = self._attrs[name]
+        except KeyError:
+            raise xml.dom.NotFoundErr()
+        self.removeAttributeNode(attr)
+
+    def removeAttributeNS(self, namespaceURI, localName):
+        if self._attrsNS is None:
+            raise xml.dom.NotFoundErr()
+        try:
+            attr = self._attrsNS[(namespaceURI, localName)]
+        except KeyError:
+            raise xml.dom.NotFoundErr()
+        self.removeAttributeNode(attr)
+
+    def removeAttributeNode(self, node):
+        if node is None:
+            raise xml.dom.NotFoundErr()
+        try:
+            self._attrs[node.name]
+        except KeyError:
+            raise xml.dom.NotFoundErr()
+        _clear_id_cache(self)
+        node.unlink()
+        # Restore this since the node is still useful and otherwise
+        # unlinked
+        node.ownerDocument = self.ownerDocument
+
+    removeAttributeNodeNS = removeAttributeNode
+
+    def hasAttribute(self, name):
+        if self._attrs is None:
+            return False
+        return name in self._attrs
+
+    def hasAttributeNS(self, namespaceURI, localName):
+        if self._attrsNS is None:
+            return False
+        return (namespaceURI, localName) in self._attrsNS
+
+    def getElementsByTagName(self, name):
+        return _get_elements_by_tagName_helper(self, name, NodeList())
+
+    def getElementsByTagNameNS(self, namespaceURI, localName):
+        return _get_elements_by_tagName_ns_helper(
+            self, namespaceURI, localName, NodeList())
+
+    def __repr__(self):
+        return "<DOM Element: %s at %#x>" % (self.tagName, id(self))
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        # indent = current indentation
+        # addindent = indentation to add to higher levels
+        # newl = newline string
+        writer.write(indent+"<" + self.tagName)
+
+        attrs = self._get_attributes()
+        a_names = sorted(attrs.keys())
+
+        for a_name in a_names:
+            writer.write(" %s=\"" % a_name)
+            _write_data(writer, attrs[a_name].value)
+            writer.write("\"")
+        if self.childNodes:
+            writer.write(">")
+            if (len(self.childNodes) == 1 and
+                self.childNodes[0].nodeType == Node.TEXT_NODE):
+                self.childNodes[0].writexml(writer, '', '', '')
+            else:
+                writer.write(newl)
+                for node in self.childNodes:
+                    node.writexml(writer, indent+addindent, addindent, newl)
+                writer.write(indent)
+            writer.write("</%s>%s" % (self.tagName, newl))
+        else:
+            writer.write("/>%s"%(newl))
+
+    def _get_attributes(self):
+        self._ensure_attributes()
+        return NamedNodeMap(self._attrs, self._attrsNS, self)
+
+    def hasAttributes(self):
+        if self._attrs:
+            return True
+        else:
+            return False
+
+    # DOM Level 3 attributes, based on the 22 Oct 2002 draft
+
+    def setIdAttribute(self, name):
+        idAttr = self.getAttributeNode(name)
+        self.setIdAttributeNode(idAttr)
+
+    def setIdAttributeNS(self, namespaceURI, localName):
+        idAttr = self.getAttributeNodeNS(namespaceURI, localName)
+        self.setIdAttributeNode(idAttr)
+
+    def setIdAttributeNode(self, idAttr):
+        if idAttr is None or not self.isSameNode(idAttr.ownerElement):
+            raise xml.dom.NotFoundErr()
+        if _get_containing_entref(self) is not None:
+            raise xml.dom.NoModificationAllowedErr()
+        if not idAttr._is_id:
+            idAttr._is_id = True
+            self._magic_id_nodes += 1
+            self.ownerDocument._magic_id_count += 1
+            _clear_id_cache(self)
+
+defproperty(Element, "attributes",
+            doc="NamedNodeMap of attributes on the element.")
+defproperty(Element, "localName",
+            doc="Namespace-local name of this element.")
+
+
+def _set_attribute_node(element, attr):
+    _clear_id_cache(element)
+    element._ensure_attributes()
+    element._attrs[attr.name] = attr
+    element._attrsNS[(attr.namespaceURI, attr.localName)] = attr
+
+    # This creates a circular reference, but Element.unlink()
+    # breaks the cycle since the references to the attribute
+    # dictionaries are tossed.
+    attr.ownerElement = element
+
+class Childless:
+    """Mixin that makes childless-ness easy to implement and avoids
+    the complexity of the Node methods that deal with children.
+    """
+    __slots__ = ()
+
+    attributes = None
+    childNodes = EmptyNodeList()
+    firstChild = None
+    lastChild = None
+
+    def _get_firstChild(self):
+        return None
+
+    def _get_lastChild(self):
+        return None
+
+    def appendChild(self, node):
+        raise xml.dom.HierarchyRequestErr(
+            self.nodeName + " nodes cannot have children")
+
+    def hasChildNodes(self):
+        return False
+
+    def insertBefore(self, newChild, refChild):
+        raise xml.dom.HierarchyRequestErr(
+            self.nodeName + " nodes do not have children")
+
+    def removeChild(self, oldChild):
+        raise xml.dom.NotFoundErr(
+            self.nodeName + " nodes do not have children")
+
+    def normalize(self):
+        # For childless nodes, normalize() has nothing to do.
+        pass
+
+    def replaceChild(self, newChild, oldChild):
+        raise xml.dom.HierarchyRequestErr(
+            self.nodeName + " nodes do not have children")
+
+
+class ProcessingInstruction(Childless, Node):
+    nodeType = Node.PROCESSING_INSTRUCTION_NODE
+    __slots__ = ('target', 'data')
+
+    def __init__(self, target, data):
+        self.target = target
+        self.data = data
+
+    # nodeValue is an alias for data
+    def _get_nodeValue(self):
+        return self.data
+    def _set_nodeValue(self, value):
+        self.data = value
+    nodeValue = property(_get_nodeValue, _set_nodeValue)
+
+    # nodeName is an alias for target
+    def _get_nodeName(self):
+        return self.target
+    def _set_nodeName(self, value):
+        self.target = value
+    nodeName = property(_get_nodeName, _set_nodeName)
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        writer.write("%s<?%s %s?>%s" % (indent,self.target, self.data, newl))
+
+
+class CharacterData(Childless, Node):
+    __slots__=('_data', 'ownerDocument','parentNode', 'previousSibling', 'nextSibling')
+
+    def __init__(self):
+        self.ownerDocument = self.parentNode = None
+        self.previousSibling = self.nextSibling = None
+        self._data = ''
+        Node.__init__(self)
+
+    def _get_length(self):
+        return len(self.data)
+    __len__ = _get_length
+
+    def _get_data(self):
+        return self._data
+    def _set_data(self, data):
+        self._data = data
+
+    data = nodeValue = property(_get_data, _set_data)
+
+    def __repr__(self):
+        data = self.data
+        if len(data) > 10:
+            dotdotdot = "..."
+        else:
+            dotdotdot = ""
+        return '<DOM %s node "%r%s">' % (
+            self.__class__.__name__, data[0:10], dotdotdot)
+
+    def substringData(self, offset, count):
+        if offset < 0:
+            raise xml.dom.IndexSizeErr("offset cannot be negative")
+        if offset >= len(self.data):
+            raise xml.dom.IndexSizeErr("offset cannot be beyond end of data")
+        if count < 0:
+            raise xml.dom.IndexSizeErr("count cannot be negative")
+        return self.data[offset:offset+count]
+
+    def appendData(self, arg):
+        self.data = self.data + arg
+
+    def insertData(self, offset, arg):
+        if offset < 0:
+            raise xml.dom.IndexSizeErr("offset cannot be negative")
+        if offset >= len(self.data):
+            raise xml.dom.IndexSizeErr("offset cannot be beyond end of data")
+        if arg:
+            self.data = "%s%s%s" % (
+                self.data[:offset], arg, self.data[offset:])
+
+    def deleteData(self, offset, count):
+        if offset < 0:
+            raise xml.dom.IndexSizeErr("offset cannot be negative")
+        if offset >= len(self.data):
+            raise xml.dom.IndexSizeErr("offset cannot be beyond end of data")
+        if count < 0:
+            raise xml.dom.IndexSizeErr("count cannot be negative")
+        if count:
+            self.data = self.data[:offset] + self.data[offset+count:]
+
+    def replaceData(self, offset, count, arg):
+        if offset < 0:
+            raise xml.dom.IndexSizeErr("offset cannot be negative")
+        if offset >= len(self.data):
+            raise xml.dom.IndexSizeErr("offset cannot be beyond end of data")
+        if count < 0:
+            raise xml.dom.IndexSizeErr("count cannot be negative")
+        if count:
+            self.data = "%s%s%s" % (
+                self.data[:offset], arg, self.data[offset+count:])
+
+defproperty(CharacterData, "length", doc="Length of the string data.")
+
+
+class Text(CharacterData):
+    __slots__ = ()
+
+    nodeType = Node.TEXT_NODE
+    nodeName = "#text"
+    attributes = None
+
+    def splitText(self, offset):
+        if offset < 0 or offset > len(self.data):
+            raise xml.dom.IndexSizeErr("illegal offset value")
+        newText = self.__class__()
+        newText.data = self.data[offset:]
+        newText.ownerDocument = self.ownerDocument
+        next = self.nextSibling
+        if self.parentNode and self in self.parentNode.childNodes:
+            if next is None:
+                self.parentNode.appendChild(newText)
+            else:
+                self.parentNode.insertBefore(newText, next)
+        self.data = self.data[:offset]
+        return newText
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        _write_data(writer, "%s%s%s" % (indent, self.data, newl))
+
+    # DOM Level 3 (WD 9 April 2002)
+
+    def _get_wholeText(self):
+        L = [self.data]
+        n = self.previousSibling
+        while n is not None:
+            if n.nodeType in (Node.TEXT_NODE, Node.CDATA_SECTION_NODE):
+                L.insert(0, n.data)
+                n = n.previousSibling
+            else:
+                break
+        n = self.nextSibling
+        while n is not None:
+            if n.nodeType in (Node.TEXT_NODE, Node.CDATA_SECTION_NODE):
+                L.append(n.data)
+                n = n.nextSibling
+            else:
+                break
+        return ''.join(L)
+
+    def replaceWholeText(self, content):
+        # XXX This needs to be seriously changed if minidom ever
+        # supports EntityReference nodes.
+        parent = self.parentNode
+        n = self.previousSibling
+        while n is not None:
+            if n.nodeType in (Node.TEXT_NODE, Node.CDATA_SECTION_NODE):
+                next = n.previousSibling
+                parent.removeChild(n)
+                n = next
+            else:
+                break
+        n = self.nextSibling
+        if not content:
+            parent.removeChild(self)
+        while n is not None:
+            if n.nodeType in (Node.TEXT_NODE, Node.CDATA_SECTION_NODE):
+                next = n.nextSibling
+                parent.removeChild(n)
+                n = next
+            else:
+                break
+        if content:
+            self.data = content
+            return self
+        else:
+            return None
+
+    def _get_isWhitespaceInElementContent(self):
+        if self.data.strip():
+            return False
+        elem = _get_containing_element(self)
+        if elem is None:
+            return False
+        info = self.ownerDocument._get_elem_info(elem)
+        if info is None:
+            return False
+        else:
+            return info.isElementContent()
+
+defproperty(Text, "isWhitespaceInElementContent",
+            doc="True iff this text node contains only whitespace"
+                " and is in element content.")
+defproperty(Text, "wholeText",
+            doc="The text of all logically-adjacent text nodes.")
+
+
+def _get_containing_element(node):
+    c = node.parentNode
+    while c is not None:
+        if c.nodeType == Node.ELEMENT_NODE:
+            return c
+        c = c.parentNode
+    return None
+
+def _get_containing_entref(node):
+    c = node.parentNode
+    while c is not None:
+        if c.nodeType == Node.ENTITY_REFERENCE_NODE:
+            return c
+        c = c.parentNode
+    return None
+
+
+class Comment(CharacterData):
+    nodeType = Node.COMMENT_NODE
+    nodeName = "#comment"
+
+    def __init__(self, data):
+        CharacterData.__init__(self)
+        self._data = data
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        if "--" in self.data:
+            raise ValueError("'--' is not allowed in a comment node")
+        writer.write("%s<!--%s-->%s" % (indent, self.data, newl))
+
+
+class CDATASection(Text):
+    __slots__ = ()
+
+    nodeType = Node.CDATA_SECTION_NODE
+    nodeName = "#cdata-section"
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        if self.data.find("]]>") >= 0:
+            raise ValueError("']]>' not allowed in a CDATA section")
+        writer.write("<![CDATA[%s]]>" % self.data)
+
+
+class ReadOnlySequentialNamedNodeMap(object):
+    __slots__ = '_seq',
+
+    def __init__(self, seq=()):
+        # seq should be a list or tuple
+        self._seq = seq
+
+    def __len__(self):
+        return len(self._seq)
+
+    def _get_length(self):
+        return len(self._seq)
+
+    def getNamedItem(self, name):
+        for n in self._seq:
+            if n.nodeName == name:
+                return n
+
+    def getNamedItemNS(self, namespaceURI, localName):
+        for n in self._seq:
+            if n.namespaceURI == namespaceURI and n.localName == localName:
+                return n
+
+    def __getitem__(self, name_or_tuple):
+        if isinstance(name_or_tuple, tuple):
+            node = self.getNamedItemNS(*name_or_tuple)
+        else:
+            node = self.getNamedItem(name_or_tuple)
+        if node is None:
+            raise KeyError(name_or_tuple)
+        return node
+
+    def item(self, index):
+        if index < 0:
+            return None
+        try:
+            return self._seq[index]
+        except IndexError:
+            return None
+
+    def removeNamedItem(self, name):
+        raise xml.dom.NoModificationAllowedErr(
+            "NamedNodeMap instance is read-only")
+
+    def removeNamedItemNS(self, namespaceURI, localName):
+        raise xml.dom.NoModificationAllowedErr(
+            "NamedNodeMap instance is read-only")
+
+    def setNamedItem(self, node):
+        raise xml.dom.NoModificationAllowedErr(
+            "NamedNodeMap instance is read-only")
+
+    def setNamedItemNS(self, node):
+        raise xml.dom.NoModificationAllowedErr(
+            "NamedNodeMap instance is read-only")
+
+    def __getstate__(self):
+        return [self._seq]
+
+    def __setstate__(self, state):
+        self._seq = state[0]
+
+defproperty(ReadOnlySequentialNamedNodeMap, "length",
+            doc="Number of entries in the NamedNodeMap.")
+
+
+class Identified:
+    """Mix-in class that supports the publicId and systemId attributes."""
+
+    __slots__ = 'publicId', 'systemId'
+
+    def _identified_mixin_init(self, publicId, systemId):
+        self.publicId = publicId
+        self.systemId = systemId
+
+    def _get_publicId(self):
+        return self.publicId
+
+    def _get_systemId(self):
+        return self.systemId
+
+class DocumentType(Identified, Childless, Node):
+    nodeType = Node.DOCUMENT_TYPE_NODE
+    nodeValue = None
+    name = None
+    publicId = None
+    systemId = None
+    internalSubset = None
+
+    def __init__(self, qualifiedName):
+        self.entities = ReadOnlySequentialNamedNodeMap()
+        self.notations = ReadOnlySequentialNamedNodeMap()
+        if qualifiedName:
+            prefix, localname = _nssplit(qualifiedName)
+            self.name = localname
+        self.nodeName = self.name
+
+    def _get_internalSubset(self):
+        return self.internalSubset
+
+    def cloneNode(self, deep):
+        if self.ownerDocument is None:
+            # it's ok
+            clone = DocumentType(None)
+            clone.name = self.name
+            clone.nodeName = self.name
+            operation = xml.dom.UserDataHandler.NODE_CLONED
+            if deep:
+                clone.entities._seq = []
+                clone.notations._seq = []
+                for n in self.notations._seq:
+                    notation = Notation(n.nodeName, n.publicId, n.systemId)
+                    clone.notations._seq.append(notation)
+                    n._call_user_data_handler(operation, n, notation)
+                for e in self.entities._seq:
+                    entity = Entity(e.nodeName, e.publicId, e.systemId,
+                                    e.notationName)
+                    entity.actualEncoding = e.actualEncoding
+                    entity.encoding = e.encoding
+                    entity.version = e.version
+                    clone.entities._seq.append(entity)
+                    e._call_user_data_handler(operation, e, entity)
+            self._call_user_data_handler(operation, self, clone)
+            return clone
+        else:
+            return None
+
+    def writexml(self, writer, indent="", addindent="", newl=""):
+        writer.write("<!DOCTYPE ")
+        writer.write(self.name)
+        if self.publicId:
+            writer.write("%s  PUBLIC '%s'%s  '%s'"
+                         % (newl, self.publicId, newl, self.systemId))
+        elif self.systemId:
+            writer.write("%s  SYSTEM '%s'" % (newl, self.systemId))
+        if self.internalSubset is not None:
+            writer.write(" [")
+            writer.write(self.internalSubset)
+            writer.write("]")
+        writer.write(">"+newl)
+
+class Entity(Identified, Node):
+    attributes = None
+    nodeType = Node.ENTITY_NODE
+    nodeValue = None
+
+    actualEncoding = None
+    encoding = None
+    version = None
+
+    def __init__(self, name, publicId, systemId, notation):
+        self.nodeName = name
+        self.notationName = notation
+        self.childNodes = NodeList()
+        self._identified_mixin_init(publicId, systemId)
+
+    def _get_actualEncoding(self):
+        return self.actualEncoding
+
+    def _get_encoding(self):
+        return self.encoding
+
+    def _get_version(self):
+        return self.version
+
+    def appendChild(self, newChild):
+        raise xml.dom.HierarchyRequestErr(
+            "cannot append children to an entity node")
+
+    def insertBefore(self, newChild, refChild):
+        raise xml.dom.HierarchyRequestErr(
+            "cannot insert children below an entity node")
+
+    def removeChild(self, oldChild):
+        raise xml.dom.HierarchyRequestErr(
+            "cannot remove children from an entity node")
+
+    def replaceChild(self, newChild, oldChild):
+        raise xml.dom.HierarchyRequestErr(
+            "cannot replace children of an entity node")
+
+class Notation(Identified, Childless, Node):
+    nodeType = Node.NOTATION_NODE
+    nodeValue = None
+
+    def __init__(self, name, publicId, systemId):
+        self.nodeName = name
+        self._identified_mixin_init(publicId, systemId)
+
+
+class DOMImplementation(DOMImplementationLS):
+    _features = [("core", "1.0"),
+                 ("core", "2.0"),
+                 ("core", None),
+                 ("xml", "1.0"),
+                 ("xml", "2.0"),
+                 ("xml", None),
+                 ("ls-load", "3.0"),
+                 ("ls-load", None),
+                 ]
+
+    def hasFeature(self, feature, version):
+        if version == "":
+            version = None
+        return (feature.lower(), version) in self._features
+
+    def createDocument(self, namespaceURI, qualifiedName, doctype):
+        if doctype and doctype.parentNode is not None:
+            raise xml.dom.WrongDocumentErr(
+                "doctype object owned by another DOM tree")
+        doc = self._create_document()
+
+        add_root_element = not (namespaceURI is None
+                                and qualifiedName is None
+                                and doctype is None)
+
+        if not qualifiedName and add_root_element:
+            # The spec is unclear what to raise here; SyntaxErr
+            # would be the other obvious candidate. Since Xerces raises
+            # InvalidCharacterErr, and since SyntaxErr is not listed
+            # for createDocument, that seems to be the better choice.
+            # XXX: need to check for illegal characters here and in
+            # createElement.
+
+            # DOM Level III clears this up when talking about the return value
+            # of this function.  If namespaceURI, qName and DocType are
+            # Null the document is returned without a document element
+            # Otherwise if doctype or namespaceURI are not None
+            # Then we go back to the above problem
+            raise xml.dom.InvalidCharacterErr("Element with no name")
+
+        if add_root_element:
+            prefix, localname = _nssplit(qualifiedName)
+            if prefix == "xml" \
+               and namespaceURI != "http://www.w3.org/XML/1998/namespace":
+                raise xml.dom.NamespaceErr("illegal use of 'xml' prefix")
+            if prefix and not namespaceURI:
+                raise xml.dom.NamespaceErr(
+                    "illegal use of prefix without namespaces")
+            element = doc.createElementNS(namespaceURI, qualifiedName)
+            if doctype:
+                doc.appendChild(doctype)
+            doc.appendChild(element)
+
+        if doctype:
+            doctype.parentNode = doctype.ownerDocument = doc
+
+        doc.doctype = doctype
+        doc.implementation = self
+        return doc
+
+    def createDocumentType(self, qualifiedName, publicId, systemId):
+        doctype = DocumentType(qualifiedName)
+        doctype.publicId = publicId
+        doctype.systemId = systemId
+        return doctype
+
+    # DOM Level 3 (WD 9 April 2002)
+
+    def getInterface(self, feature):
+        if self.hasFeature(feature, None):
+            return self
+        else:
+            return None
+
+    # internal
+    def _create_document(self):
+        return Document()
+
+class ElementInfo(object):
+    """Object that represents content-model information for an element.
+
+    This implementation is not expected to be used in practice; DOM
+    builders should provide implementations which do the right thing
+    using information available to it.
+
+    """
+
+    __slots__ = 'tagName',
+
+    def __init__(self, name):
+        self.tagName = name
+
+    def getAttributeType(self, aname):
+        return _no_type
+
+    def getAttributeTypeNS(self, namespaceURI, localName):
+        return _no_type
+
+    def isElementContent(self):
+        return False
+
+    def isEmpty(self):
+        """Returns true iff this element is declared to have an EMPTY
+        content model."""
+        return False
+
+    def isId(self, aname):
+        """Returns true iff the named attribute is a DTD-style ID."""
+        return False
+
+    def isIdNS(self, namespaceURI, localName):
+        """Returns true iff the identified attribute is a DTD-style ID."""
+        return False
+
+    def __getstate__(self):
+        return self.tagName
+
+    def __setstate__(self, state):
+        self.tagName = state
+
+def _clear_id_cache(node):
+    if node.nodeType == Node.DOCUMENT_NODE:
+        node._id_cache.clear()
+        node._id_search_stack = None
+    elif _in_document(node):
+        node.ownerDocument._id_cache.clear()
+        node.ownerDocument._id_search_stack= None
+
+class Document(Node, DocumentLS):
+    __slots__ = ('_elem_info', 'doctype',
+                 '_id_search_stack', 'childNodes', '_id_cache')
+    _child_node_types = (Node.ELEMENT_NODE, Node.PROCESSING_INSTRUCTION_NODE,
+                         Node.COMMENT_NODE, Node.DOCUMENT_TYPE_NODE)
+
+    implementation = DOMImplementation()
+    nodeType = Node.DOCUMENT_NODE
+    nodeName = "#document"
+    nodeValue = None
+    attributes = None
+    parentNode = None
+    previousSibling = nextSibling = None
+
+
+    # Document attributes from Level 3 (WD 9 April 2002)
+
+    actualEncoding = None
+    encoding = None
+    standalone = None
+    version = None
+    strictErrorChecking = False
+    errorHandler = None
+    documentURI = None
+
+    _magic_id_count = 0
+
+    def __init__(self):
+        self.doctype = None
+        self.childNodes = NodeList()
+        # mapping of (namespaceURI, localName) -> ElementInfo
+        #        and tagName -> ElementInfo
+        self._elem_info = {}
+        self._id_cache = {}
+        self._id_search_stack = None
+
+    def _get_elem_info(self, element):
+        if element.namespaceURI:
+            key = element.namespaceURI, element.localName
+        else:
+            key = element.tagName
+        return self._elem_info.get(key)
+
+    def _get_actualEncoding(self):
+        return self.actualEncoding
+
+    def _get_doctype(self):
+        return self.doctype
+
+    def _get_documentURI(self):
+        return self.documentURI
+
+    def _get_encoding(self):
+        return self.encoding
+
+    def _get_errorHandler(self):
+        return self.errorHandler
+
+    def _get_standalone(self):
+        return self.standalone
+
+    def _get_strictErrorChecking(self):
+        return self.strictErrorChecking
+
+    def _get_version(self):
+        return self.version
+
+    def appendChild(self, node):
+        if node.nodeType not in self._child_node_types:
+            raise xml.dom.HierarchyRequestErr(
+                "%s cannot be child of %s" % (repr(node), repr(self)))
+        if node.parentNode is not None:
+            # This needs to be done before the next test since this
+            # may *be* the document element, in which case it should
+            # end up re-ordered to the end.
+            node.parentNode.removeChild(node)
+
+        if node.nodeType == Node.ELEMENT_NODE \
+           and self._get_documentElement():
+            raise xml.dom.HierarchyRequestErr(
+                "two document elements disallowed")
+        return Node.appendChild(self, node)
+
+    def removeChild(self, oldChild):
+        try:
+            self.childNodes.remove(oldChild)
+        except ValueError:
+            raise xml.dom.NotFoundErr()
+        oldChild.nextSibling = oldChild.previousSibling = None
+        oldChild.parentNode = None
+        if self.documentElement is oldChild:
+            self.documentElement = None
+
+        return oldChild
+
+    def _get_documentElement(self):
+        for node in self.childNodes:
+            if node.nodeType == Node.ELEMENT_NODE:
+                return node
+
+    def unlink(self):
+        if self.doctype is not None:
+            self.doctype.unlink()
+            self.doctype = None
+        Node.unlink(self)
+
+    def cloneNode(self, deep):
+        if not deep:
+            return None
+        clone = self.implementation.createDocument(None, None, None)
+        clone.encoding = self.encoding
+        clone.standalone = self.standalone
+        clone.version = self.version
+        for n in self.childNodes:
+            childclone = _clone_node(n, deep, clone)
+            assert childclone.ownerDocument.isSameNode(clone)
+            clone.childNodes.append(childclone)
+            if childclone.nodeType == Node.DOCUMENT_NODE:
+                assert clone.documentElement is None
+            elif childclone.nodeType == Node.DOCUMENT_TYPE_NODE:
+                assert clone.doctype is None
+                clone.doctype = childclone
+            childclone.parentNode = clone
+        self._call_user_data_handler(xml.dom.UserDataHandler.NODE_CLONED,
+                                     self, clone)
+        return clone
+
+    def createDocumentFragment(self):
+        d = DocumentFragment()
+        d.ownerDocument = self
+        return d
+
+    def createElement(self, tagName):
+        e = Element(tagName)
+        e.ownerDocument = self
+        return e
+
+    def createTextNode(self, data):
+        if not isinstance(data, str):
+            raise TypeError("node contents must be a string")
+        t = Text()
+        t.data = data
+        t.ownerDocument = self
+        return t
+
+    def createCDATASection(self, data):
+        if not isinstance(data, str):
+            raise TypeError("node contents must be a string")
+        c = CDATASection()
+        c.data = data
+        c.ownerDocument = self
+        return c
+
+    def createComment(self, data):
+        c = Comment(data)
+        c.ownerDocument = self
+        return c
+
+    def createProcessingInstruction(self, target, data):
+        p = ProcessingInstruction(target, data)
+        p.ownerDocument = self
+        return p
+
+    def createAttribute(self, qName):
+        a = Attr(qName)
+        a.ownerDocument = self
+        a.value = ""
+        return a
+
+    def createElementNS(self, namespaceURI, qualifiedName):
+        prefix, localName = _nssplit(qualifiedName)
+        e = Element(qualifiedName, namespaceURI, prefix)
+        e.ownerDocument = self
+        return e
+
+    def createAttributeNS(self, namespaceURI, qualifiedName):
+        prefix, localName = _nssplit(qualifiedName)
+        a = Attr(qualifiedName, namespaceURI, localName, prefix)
+        a.ownerDocument = self
+        a.value = ""
+        return a
+
+    # A couple of implementation-specific helpers to create node types
+    # not supported by the W3C DOM specs:
+
+    def _create_entity(self, name, publicId, systemId, notationName):
+        e = Entity(name, publicId, systemId, notationName)
+        e.ownerDocument = self
+        return e
+
+    def _create_notation(self, name, publicId, systemId):
+        n = Notation(name, publicId, systemId)
+        n.ownerDocument = self
+        return n
+
+    def getElementById(self, id):
+        if id in self._id_cache:
+            return self._id_cache[id]
+        if not (self._elem_info or self._magic_id_count):
+            return None
+
+        stack = self._id_search_stack
+        if stack is None:
+            # we never searched before, or the cache has been cleared
+            stack = [self.documentElement]
+            self._id_search_stack = stack
+        elif not stack:
+            # Previous search was completed and cache is still valid;
+            # no matching node.
+            return None
+
+        result = None
+        while stack:
+            node = stack.pop()
+            # add child elements to stack for continued searching
+            stack.extend([child for child in node.childNodes
+                          if child.nodeType in _nodeTypes_with_children])
+            # check this node
+            info = self._get_elem_info(node)
+            if info:
+                # We have to process all ID attributes before
+                # returning in order to get all the attributes set to
+                # be IDs using Element.setIdAttribute*().
+                for attr in node.attributes.values():
+                    if attr.namespaceURI:
+                        if info.isIdNS(attr.namespaceURI, attr.localName):
+                            self._id_cache[attr.value] = node
+                            if attr.value == id:
+                                result = node
+                            elif not node._magic_id_nodes:
+                                break
+                    elif info.isId(attr.name):
+                        self._id_cache[attr.value] = node
+                        if attr.value == id:
+                            result = node
+                        elif not node._magic_id_nodes:
+                            break
+                    elif attr._is_id:
+                        self._id_cache[attr.value] = node
+                        if attr.value == id:
+                            result = node
+                        elif node._magic_id_nodes == 1:
+                            break
+            elif node._magic_id_nodes:
+                for attr in node.attributes.values():
+                    if attr._is_id:
+                        self._id_cache[attr.value] = node
+                        if attr.value == id:
+                            result = node
+            if result is not None:
+                break
+        return result
+
+    def getElementsByTagName(self, name):
+        return _get_elements_by_tagName_helper(self, name, NodeList())
+
+    def getElementsByTagNameNS(self, namespaceURI, localName):
+        return _get_elements_by_tagName_ns_helper(
+            self, namespaceURI, localName, NodeList())
+
+    def isSupported(self, feature, version):
+        return self.implementation.hasFeature(feature, version)
+
+    def importNode(self, node, deep):
+        if node.nodeType == Node.DOCUMENT_NODE:
+            raise xml.dom.NotSupportedErr("cannot import document nodes")
+        elif node.nodeType == Node.DOCUMENT_TYPE_NODE:
+            raise xml.dom.NotSupportedErr("cannot import document type nodes")
+        return _clone_node(node, deep, self)
+
+    def writexml(self, writer, indent="", addindent="", newl="", encoding=None):
+        if encoding is None:
+            writer.write('<?xml version="1.0" ?>'+newl)
+        else:
+            writer.write('<?xml version="1.0" encoding="%s"?>%s' % (
+                encoding, newl))
+        for node in self.childNodes:
+            node.writexml(writer, indent, addindent, newl)
+
+    # DOM Level 3 (WD 9 April 2002)
+
+    def renameNode(self, n, namespaceURI, name):
+        if n.ownerDocument is not self:
+            raise xml.dom.WrongDocumentErr(
+                "cannot rename nodes from other documents;\n"
+                "expected %s,\nfound %s" % (self, n.ownerDocument))
+        if n.nodeType not in (Node.ELEMENT_NODE, Node.ATTRIBUTE_NODE):
+            raise xml.dom.NotSupportedErr(
+                "renameNode() only applies to element and attribute nodes")
+        if namespaceURI != EMPTY_NAMESPACE:
+            if ':' in name:
+                prefix, localName = name.split(':', 1)
+                if (  prefix == "xmlns"
+                      and namespaceURI != xml.dom.XMLNS_NAMESPACE):
+                    raise xml.dom.NamespaceErr(
+                        "illegal use of 'xmlns' prefix")
+            else:
+                if (  name == "xmlns"
+                      and namespaceURI != xml.dom.XMLNS_NAMESPACE
+                      and n.nodeType == Node.ATTRIBUTE_NODE):
+                    raise xml.dom.NamespaceErr(
+                        "illegal use of the 'xmlns' attribute")
+                prefix = None
+                localName = name
+        else:
+            prefix = None
+            localName = None
+        if n.nodeType == Node.ATTRIBUTE_NODE:
+            element = n.ownerElement
+            if element is not None:
+                is_id = n._is_id
+                element.removeAttributeNode(n)
+        else:
+            element = None
+        n.prefix = prefix
+        n._localName = localName
+        n.namespaceURI = namespaceURI
+        n.nodeName = name
+        if n.nodeType == Node.ELEMENT_NODE:
+            n.tagName = name
+        else:
+            # attribute node
+            n.name = name
+            if element is not None:
+                element.setAttributeNode(n)
+                if is_id:
+                    element.setIdAttributeNode(n)
+        # It's not clear from a semantic perspective whether we should
+        # call the user data handlers for the NODE_RENAMED event since
+        # we're re-using the existing node.  The draft spec has been
+        # interpreted as meaning "no, don't call the handler unless a
+        # new node is created."
+        return n
+
+defproperty(Document, "documentElement",
+            doc="Top-level element of this document.")
+
+
+def _clone_node(node, deep, newOwnerDocument):
+    """
+    Clone a node and give it the new owner document.
+    Called by Node.cloneNode and Document.importNode
+    """
+    if node.ownerDocument.isSameNode(newOwnerDocument):
+        operation = xml.dom.UserDataHandler.NODE_CLONED
+    else:
+        operation = xml.dom.UserDataHandler.NODE_IMPORTED
+    if node.nodeType == Node.ELEMENT_NODE:
+        clone = newOwnerDocument.createElementNS(node.namespaceURI,
+                                                 node.nodeName)
+        for attr in node.attributes.values():
+            clone.setAttributeNS(attr.namespaceURI, attr.nodeName, attr.value)
+            a = clone.getAttributeNodeNS(attr.namespaceURI, attr.localName)
+            a.specified = attr.specified
+
+        if deep:
+            for child in node.childNodes:
+                c = _clone_node(child, deep, newOwnerDocument)
+                clone.appendChild(c)
+
+    elif node.nodeType == Node.DOCUMENT_FRAGMENT_NODE:
+        clone = newOwnerDocument.createDocumentFragment()
+        if deep:
+            for child in node.childNodes:
+                c = _clone_node(child, deep, newOwnerDocument)
+                clone.appendChild(c)
+
+    elif node.nodeType == Node.TEXT_NODE:
+        clone = newOwnerDocument.createTextNode(node.data)
+    elif node.nodeType == Node.CDATA_SECTION_NODE:
+        clone = newOwnerDocument.createCDATASection(node.data)
+    elif node.nodeType == Node.PROCESSING_INSTRUCTION_NODE:
+        clone = newOwnerDocument.createProcessingInstruction(node.target,
+                                                             node.data)
+    elif node.nodeType == Node.COMMENT_NODE:
+        clone = newOwnerDocument.createComment(node.data)
+    elif node.nodeType == Node.ATTRIBUTE_NODE:
+        clone = newOwnerDocument.createAttributeNS(node.namespaceURI,
+                                                   node.nodeName)
+        clone.specified = True
+        clone.value = node.value
+    elif node.nodeType == Node.DOCUMENT_TYPE_NODE:
+        assert node.ownerDocument is not newOwnerDocument
+        operation = xml.dom.UserDataHandler.NODE_IMPORTED
+        clone = newOwnerDocument.implementation.createDocumentType(
+            node.name, node.publicId, node.systemId)
+        clone.ownerDocument = newOwnerDocument
+        if deep:
+            clone.entities._seq = []
+            clone.notations._seq = []
+            for n in node.notations._seq:
+                notation = Notation(n.nodeName, n.publicId, n.systemId)
+                notation.ownerDocument = newOwnerDocument
+                clone.notations._seq.append(notation)
+                if hasattr(n, '_call_user_data_handler'):
+                    n._call_user_data_handler(operation, n, notation)
+            for e in node.entities._seq:
+                entity = Entity(e.nodeName, e.publicId, e.systemId,
+                                e.notationName)
+                entity.actualEncoding = e.actualEncoding
+                entity.encoding = e.encoding
+                entity.version = e.version
+                entity.ownerDocument = newOwnerDocument
+                clone.entities._seq.append(entity)
+                if hasattr(e, '_call_user_data_handler'):
+                    e._call_user_data_handler(operation, e, entity)
+    else:
+        # Note the cloning of Document and DocumentType nodes is
+        # implementation specific.  minidom handles those cases
+        # directly in the cloneNode() methods.
+        raise xml.dom.NotSupportedErr("Cannot clone node %s" % repr(node))
+
+    # Check for _call_user_data_handler() since this could conceivably
+    # used with other DOM implementations (one of the FourThought
+    # DOMs, perhaps?).
+    if hasattr(node, '_call_user_data_handler'):
+        node._call_user_data_handler(operation, node, clone)
+    return clone
+
+
+def _nssplit(qualifiedName):
+    fields = qualifiedName.split(':', 1)
+    if len(fields) == 2:
+        return fields
+    else:
+        return (None, fields[0])
+
+
+def _do_pulldom_parse(func, args, kwargs):
+    events = func(*args, **kwargs)
+    toktype, rootNode = events.getEvent()
+    events.expandNode(rootNode)
+    events.clear()
+    return rootNode
+
+def parse(file, parser=None, bufsize=None):
+    """Parse a file into a DOM by filename or file object."""
+    if parser is None and not bufsize:
+        from xml.dom import expatbuilder
+        return expatbuilder.parse(file)
+    else:
+        from xml.dom import pulldom
+        return _do_pulldom_parse(pulldom.parse, (file,),
+            {'parser': parser, 'bufsize': bufsize})
+
+def parseString(string, parser=None):
+    """Parse a file into a DOM from a string."""
+    if parser is None:
+        from xml.dom import expatbuilder
+        return expatbuilder.parseString(string)
+    else:
+        from xml.dom import pulldom
+        return _do_pulldom_parse(pulldom.parseString, (string,),
+                                 {'parser': parser})
+
+def getDOMImplementation(features=None):
+    if features:
+        if isinstance(features, str):
+            features = domreg._parse_feature_string(features)
+        for f, v in features:
+            if not Document.implementation.hasFeature(f, v):
+                return None
+    return Document.implementation
diff --git a/Lib/xml/dom/pulldom.py b/Lib/xml/dom/pulldom.py
new file mode 100644
index 000000000..43504f765
--- /dev/null
+++ b/Lib/xml/dom/pulldom.py
@@ -0,0 +1,342 @@
+import xml.sax
+import xml.sax.handler
+
+START_ELEMENT = "START_ELEMENT"
+END_ELEMENT = "END_ELEMENT"
+COMMENT = "COMMENT"
+START_DOCUMENT = "START_DOCUMENT"
+END_DOCUMENT = "END_DOCUMENT"
+PROCESSING_INSTRUCTION = "PROCESSING_INSTRUCTION"
+IGNORABLE_WHITESPACE = "IGNORABLE_WHITESPACE"
+CHARACTERS = "CHARACTERS"
+
+class PullDOM(xml.sax.ContentHandler):
+    _locator = None
+    document = None
+
+    def __init__(self, documentFactory=None):
+        from xml.dom import XML_NAMESPACE
+        self.documentFactory = documentFactory
+        self.firstEvent = [None, None]
+        self.lastEvent = self.firstEvent
+        self.elementStack = []
+        self.push = self.elementStack.append
+        try:
+            self.pop = self.elementStack.pop
+        except AttributeError:
+            # use class' pop instead
+            pass
+        self._ns_contexts = [{XML_NAMESPACE:'xml'}] # contains uri -> prefix dicts
+        self._current_context = self._ns_contexts[-1]
+        self.pending_events = []
+
+    def pop(self):
+        result = self.elementStack[-1]
+        del self.elementStack[-1]
+        return result
+
+    def setDocumentLocator(self, locator):
+        self._locator = locator
+
+    def startPrefixMapping(self, prefix, uri):
+        if not hasattr(self, '_xmlns_attrs'):
+            self._xmlns_attrs = []
+        self._xmlns_attrs.append((prefix or 'xmlns', uri))
+        self._ns_contexts.append(self._current_context.copy())
+        self._current_context[uri] = prefix or None
+
+    def endPrefixMapping(self, prefix):
+        self._current_context = self._ns_contexts.pop()
+
+    def startElementNS(self, name, tagName , attrs):
+        # Retrieve xml namespace declaration attributes.
+        xmlns_uri = 'http://www.w3.org/2000/xmlns/'
+        xmlns_attrs = getattr(self, '_xmlns_attrs', None)
+        if xmlns_attrs is not None:
+            for aname, value in xmlns_attrs:
+                attrs._attrs[(xmlns_uri, aname)] = value
+            self._xmlns_attrs = []
+        uri, localname = name
+        if uri:
+            # When using namespaces, the reader may or may not
+            # provide us with the original name. If not, create
+            # *a* valid tagName from the current context.
+            if tagName is None:
+                prefix = self._current_context[uri]
+                if prefix:
+                    tagName = prefix + ":" + localname
+                else:
+                    tagName = localname
+            if self.document:
+                node = self.document.createElementNS(uri, tagName)
+            else:
+                node = self.buildDocument(uri, tagName)
+        else:
+            # When the tagname is not prefixed, it just appears as
+            # localname
+            if self.document:
+                node = self.document.createElement(localname)
+            else:
+                node = self.buildDocument(None, localname)
+
+        for aname,value in attrs.items():
+            a_uri, a_localname = aname
+            if a_uri == xmlns_uri:
+                if a_localname == 'xmlns':
+                    qname = a_localname
+                else:
+                    qname = 'xmlns:' + a_localname
+                attr = self.document.createAttributeNS(a_uri, qname)
+                node.setAttributeNodeNS(attr)
+            elif a_uri:
+                prefix = self._current_context[a_uri]
+                if prefix:
+                    qname = prefix + ":" + a_localname
+                else:
+                    qname = a_localname
+                attr = self.document.createAttributeNS(a_uri, qname)
+                node.setAttributeNodeNS(attr)
+            else:
+                attr = self.document.createAttribute(a_localname)
+                node.setAttributeNode(attr)
+            attr.value = value
+
+        self.lastEvent[1] = [(START_ELEMENT, node), None]
+        self.lastEvent = self.lastEvent[1]
+        self.push(node)
+
+    def endElementNS(self, name, tagName):
+        self.lastEvent[1] = [(END_ELEMENT, self.pop()), None]
+        self.lastEvent = self.lastEvent[1]
+
+    def startElement(self, name, attrs):
+        if self.document:
+            node = self.document.createElement(name)
+        else:
+            node = self.buildDocument(None, name)
+
+        for aname,value in attrs.items():
+            attr = self.document.createAttribute(aname)
+            attr.value = value
+            node.setAttributeNode(attr)
+
+        self.lastEvent[1] = [(START_ELEMENT, node), None]
+        self.lastEvent = self.lastEvent[1]
+        self.push(node)
+
+    def endElement(self, name):
+        self.lastEvent[1] = [(END_ELEMENT, self.pop()), None]
+        self.lastEvent = self.lastEvent[1]
+
+    def comment(self, s):
+        if self.document:
+            node = self.document.createComment(s)
+            self.lastEvent[1] = [(COMMENT, node), None]
+            self.lastEvent = self.lastEvent[1]
+        else:
+            event = [(COMMENT, s), None]
+            self.pending_events.append(event)
+
+    def processingInstruction(self, target, data):
+        if self.document:
+            node = self.document.createProcessingInstruction(target, data)
+            self.lastEvent[1] = [(PROCESSING_INSTRUCTION, node), None]
+            self.lastEvent = self.lastEvent[1]
+        else:
+            event = [(PROCESSING_INSTRUCTION, target, data), None]
+            self.pending_events.append(event)
+
+    def ignorableWhitespace(self, chars):
+        node = self.document.createTextNode(chars)
+        self.lastEvent[1] = [(IGNORABLE_WHITESPACE, node), None]
+        self.lastEvent = self.lastEvent[1]
+
+    def characters(self, chars):
+        node = self.document.createTextNode(chars)
+        self.lastEvent[1] = [(CHARACTERS, node), None]
+        self.lastEvent = self.lastEvent[1]
+
+    def startDocument(self):
+        if self.documentFactory is None:
+            import xml.dom.minidom
+            self.documentFactory = xml.dom.minidom.Document.implementation
+
+    def buildDocument(self, uri, tagname):
+        # Can't do that in startDocument, since we need the tagname
+        # XXX: obtain DocumentType
+        node = self.documentFactory.createDocument(uri, tagname, None)
+        self.document = node
+        self.lastEvent[1] = [(START_DOCUMENT, node), None]
+        self.lastEvent = self.lastEvent[1]
+        self.push(node)
+        # Put everything we have seen so far into the document
+        for e in self.pending_events:
+            if e[0][0] == PROCESSING_INSTRUCTION:
+                _,target,data = e[0]
+                n = self.document.createProcessingInstruction(target, data)
+                e[0] = (PROCESSING_INSTRUCTION, n)
+            elif e[0][0] == COMMENT:
+                n = self.document.createComment(e[0][1])
+                e[0] = (COMMENT, n)
+            else:
+                raise AssertionError("Unknown pending event ",e[0][0])
+            self.lastEvent[1] = e
+            self.lastEvent = e
+        self.pending_events = None
+        return node.firstChild
+
+    def endDocument(self):
+        self.lastEvent[1] = [(END_DOCUMENT, self.document), None]
+        self.pop()
+
+    def clear(self):
+        "clear(): Explicitly release parsing structures"
+        self.document = None
+
+class ErrorHandler:
+    def warning(self, exception):
+        print(exception)
+    def error(self, exception):
+        raise exception
+    def fatalError(self, exception):
+        raise exception
+
+class DOMEventStream:
+    def __init__(self, stream, parser, bufsize):
+        self.stream = stream
+        self.parser = parser
+        self.bufsize = bufsize
+        if not hasattr(self.parser, 'feed'):
+            self.getEvent = self._slurp
+        self.reset()
+
+    def reset(self):
+        self.pulldom = PullDOM()
+        # This content handler relies on namespace support
+        self.parser.setFeature(xml.sax.handler.feature_namespaces, 1)
+        self.parser.setContentHandler(self.pulldom)
+
+    def __getitem__(self, pos):
+        rc = self.getEvent()
+        if rc:
+            return rc
+        raise IndexError
+
+    def __next__(self):
+        rc = self.getEvent()
+        if rc:
+            return rc
+        raise StopIteration
+
+    def __iter__(self):
+        return self
+
+    def expandNode(self, node):
+        event = self.getEvent()
+        parents = [node]
+        while event:
+            token, cur_node = event
+            if cur_node is node:
+                return
+            if token != END_ELEMENT:
+                parents[-1].appendChild(cur_node)
+            if token == START_ELEMENT:
+                parents.append(cur_node)
+            elif token == END_ELEMENT:
+                del parents[-1]
+            event = self.getEvent()
+
+    def getEvent(self):
+        # use IncrementalParser interface, so we get the desired
+        # pull effect
+        if not self.pulldom.firstEvent[1]:
+            self.pulldom.lastEvent = self.pulldom.firstEvent
+        while not self.pulldom.firstEvent[1]:
+            buf = self.stream.read(self.bufsize)
+            if not buf:
+                self.parser.close()
+                return None
+            self.parser.feed(buf)
+        rc = self.pulldom.firstEvent[1][0]
+        self.pulldom.firstEvent[1] = self.pulldom.firstEvent[1][1]
+        return rc
+
+    def _slurp(self):
+        """ Fallback replacement for getEvent() using the
+            standard SAX2 interface, which means we slurp the
+            SAX events into memory (no performance gain, but
+            we are compatible to all SAX parsers).
+        """
+        self.parser.parse(self.stream)
+        self.getEvent = self._emit
+        return self._emit()
+
+    def _emit(self):
+        """ Fallback replacement for getEvent() that emits
+            the events that _slurp() read previously.
+        """
+        rc = self.pulldom.firstEvent[1][0]
+        self.pulldom.firstEvent[1] = self.pulldom.firstEvent[1][1]
+        return rc
+
+    def clear(self):
+        """clear(): Explicitly release parsing objects"""
+        self.pulldom.clear()
+        del self.pulldom
+        self.parser = None
+        self.stream = None
+
+class SAX2DOM(PullDOM):
+
+    def startElementNS(self, name, tagName , attrs):
+        PullDOM.startElementNS(self, name, tagName, attrs)
+        curNode = self.elementStack[-1]
+        parentNode = self.elementStack[-2]
+        parentNode.appendChild(curNode)
+
+    def startElement(self, name, attrs):
+        PullDOM.startElement(self, name, attrs)
+        curNode = self.elementStack[-1]
+        parentNode = self.elementStack[-2]
+        parentNode.appendChild(curNode)
+
+    def processingInstruction(self, target, data):
+        PullDOM.processingInstruction(self, target, data)
+        node = self.lastEvent[0][1]
+        parentNode = self.elementStack[-1]
+        parentNode.appendChild(node)
+
+    def ignorableWhitespace(self, chars):
+        PullDOM.ignorableWhitespace(self, chars)
+        node = self.lastEvent[0][1]
+        parentNode = self.elementStack[-1]
+        parentNode.appendChild(node)
+
+    def characters(self, chars):
+        PullDOM.characters(self, chars)
+        node = self.lastEvent[0][1]
+        parentNode = self.elementStack[-1]
+        parentNode.appendChild(node)
+
+
+default_bufsize = (2 ** 14) - 20
+
+def parse(stream_or_string, parser=None, bufsize=None):
+    if bufsize is None:
+        bufsize = default_bufsize
+    if isinstance(stream_or_string, str):
+        stream = open(stream_or_string, 'rb')
+    else:
+        stream = stream_or_string
+    if not parser:
+        parser = xml.sax.make_parser()
+    return DOMEventStream(stream, parser, bufsize)
+
+def parseString(string, parser=None):
+    from io import StringIO
+
+    bufsize = len(string)
+    buf = StringIO(string)
+    if not parser:
+        parser = xml.sax.make_parser()
+    return DOMEventStream(buf, parser, bufsize)
diff --git a/Lib/xml/dom/xmlbuilder.py b/Lib/xml/dom/xmlbuilder.py
new file mode 100644
index 000000000..e9a153647
--- /dev/null
+++ b/Lib/xml/dom/xmlbuilder.py
@@ -0,0 +1,410 @@
+"""Implementation of the DOM Level 3 'LS-Load' feature."""
+
+import copy
+import warnings
+import xml.dom
+
+from xml.dom.NodeFilter import NodeFilter
+
+
+__all__ = ["DOMBuilder", "DOMEntityResolver", "DOMInputSource"]
+
+
+class Options:
+    """Features object that has variables set for each DOMBuilder feature.
+
+    The DOMBuilder class uses an instance of this class to pass settings to
+    the ExpatBuilder class.
+    """
+
+    # Note that the DOMBuilder class in LoadSave constrains which of these
+    # values can be set using the DOM Level 3 LoadSave feature.
+
+    namespaces = 1
+    namespace_declarations = True
+    validation = False
+    external_parameter_entities = True
+    external_general_entities = True
+    external_dtd_subset = True
+    validate_if_schema = False
+    validate = False
+    datatype_normalization = False
+    create_entity_ref_nodes = True
+    entities = True
+    whitespace_in_element_content = True
+    cdata_sections = True
+    comments = True
+    charset_overrides_xml_encoding = True
+    infoset = False
+    supported_mediatypes_only = False
+
+    errorHandler = None
+    filter = None
+
+
+class DOMBuilder:
+    entityResolver = None
+    errorHandler = None
+    filter = None
+
+    ACTION_REPLACE = 1
+    ACTION_APPEND_AS_CHILDREN = 2
+    ACTION_INSERT_AFTER = 3
+    ACTION_INSERT_BEFORE = 4
+
+    _legal_actions = (ACTION_REPLACE, ACTION_APPEND_AS_CHILDREN,
+                      ACTION_INSERT_AFTER, ACTION_INSERT_BEFORE)
+
+    def __init__(self):
+        self._options = Options()
+
+    def _get_entityResolver(self):
+        return self.entityResolver
+    def _set_entityResolver(self, entityResolver):
+        self.entityResolver = entityResolver
+
+    def _get_errorHandler(self):
+        return self.errorHandler
+    def _set_errorHandler(self, errorHandler):
+        self.errorHandler = errorHandler
+
+    def _get_filter(self):
+        return self.filter
+    def _set_filter(self, filter):
+        self.filter = filter
+
+    def setFeature(self, name, state):
+        if self.supportsFeature(name):
+            state = state and 1 or 0
+            try:
+                settings = self._settings[(_name_xform(name), state)]
+            except KeyError:
+                raise xml.dom.NotSupportedErr(
+                    "unsupported feature: %r" % (name,))
+            else:
+                for name, value in settings:
+                    setattr(self._options, name, value)
+        else:
+            raise xml.dom.NotFoundErr("unknown feature: " + repr(name))
+
+    def supportsFeature(self, name):
+        return hasattr(self._options, _name_xform(name))
+
+    def canSetFeature(self, name, state):
+        key = (_name_xform(name), state and 1 or 0)
+        return key in self._settings
+
+    # This dictionary maps from (feature,value) to a list of
+    # (option,value) pairs that should be set on the Options object.
+    # If a (feature,value) setting is not in this dictionary, it is
+    # not supported by the DOMBuilder.
+    #
+    _settings = {
+        ("namespace_declarations", 0): [
+            ("namespace_declarations", 0)],
+        ("namespace_declarations", 1): [
+            ("namespace_declarations", 1)],
+        ("validation", 0): [
+            ("validation", 0)],
+        ("external_general_entities", 0): [
+            ("external_general_entities", 0)],
+        ("external_general_entities", 1): [
+            ("external_general_entities", 1)],
+        ("external_parameter_entities", 0): [
+            ("external_parameter_entities", 0)],
+        ("external_parameter_entities", 1): [
+            ("external_parameter_entities", 1)],
+        ("validate_if_schema", 0): [
+            ("validate_if_schema", 0)],
+        ("create_entity_ref_nodes", 0): [
+            ("create_entity_ref_nodes", 0)],
+        ("create_entity_ref_nodes", 1): [
+            ("create_entity_ref_nodes", 1)],
+        ("entities", 0): [
+            ("create_entity_ref_nodes", 0),
+            ("entities", 0)],
+        ("entities", 1): [
+            ("entities", 1)],
+        ("whitespace_in_element_content", 0): [
+            ("whitespace_in_element_content", 0)],
+        ("whitespace_in_element_content", 1): [
+            ("whitespace_in_element_content", 1)],
+        ("cdata_sections", 0): [
+            ("cdata_sections", 0)],
+        ("cdata_sections", 1): [
+            ("cdata_sections", 1)],
+        ("comments", 0): [
+            ("comments", 0)],
+        ("comments", 1): [
+            ("comments", 1)],
+        ("charset_overrides_xml_encoding", 0): [
+            ("charset_overrides_xml_encoding", 0)],
+        ("charset_overrides_xml_encoding", 1): [
+            ("charset_overrides_xml_encoding", 1)],
+        ("infoset", 0): [],
+        ("infoset", 1): [
+            ("namespace_declarations", 0),
+            ("validate_if_schema", 0),
+            ("create_entity_ref_nodes", 0),
+            ("entities", 0),
+            ("cdata_sections", 0),
+            ("datatype_normalization", 1),
+            ("whitespace_in_element_content", 1),
+            ("comments", 1),
+            ("charset_overrides_xml_encoding", 1)],
+        ("supported_mediatypes_only", 0): [
+            ("supported_mediatypes_only", 0)],
+        ("namespaces", 0): [
+            ("namespaces", 0)],
+        ("namespaces", 1): [
+            ("namespaces", 1)],
+    }
+
+    def getFeature(self, name):
+        xname = _name_xform(name)
+        try:
+            return getattr(self._options, xname)
+        except AttributeError:
+            if name == "infoset":
+                options = self._options
+                return (options.datatype_normalization
+                        and options.whitespace_in_element_content
+                        and options.comments
+                        and options.charset_overrides_xml_encoding
+                        and not (options.namespace_declarations
+                                 or options.validate_if_schema
+                                 or options.create_entity_ref_nodes
+                                 or options.entities
+                                 or options.cdata_sections))
+            raise xml.dom.NotFoundErr("feature %s not known" % repr(name))
+
+    def parseURI(self, uri):
+        if self.entityResolver:
+            input = self.entityResolver.resolveEntity(None, uri)
+        else:
+            input = DOMEntityResolver().resolveEntity(None, uri)
+        return self.parse(input)
+
+    def parse(self, input):
+        options = copy.copy(self._options)
+        options.filter = self.filter
+        options.errorHandler = self.errorHandler
+        fp = input.byteStream
+        if fp is None and options.systemId:
+            import urllib.request
+            fp = urllib.request.urlopen(input.systemId)
+        return self._parse_bytestream(fp, options)
+
+    def parseWithContext(self, input, cnode, action):
+        if action not in self._legal_actions:
+            raise ValueError("not a legal action")
+        raise NotImplementedError("Haven't written this yet...")
+
+    def _parse_bytestream(self, stream, options):
+        import xml.dom.expatbuilder
+        builder = xml.dom.expatbuilder.makeBuilder(options)
+        return builder.parseFile(stream)
+
+
+def _name_xform(name):
+    return name.lower().replace('-', '_')
+
+
+class DOMEntityResolver(object):
+    __slots__ = '_opener',
+
+    def resolveEntity(self, publicId, systemId):
+        assert systemId is not None
+        source = DOMInputSource()
+        source.publicId = publicId
+        source.systemId = systemId
+        source.byteStream = self._get_opener().open(systemId)
+
+        # determine the encoding if the transport provided it
+        source.encoding = self._guess_media_encoding(source)
+
+        # determine the base URI is we can
+        import posixpath, urllib.parse
+        parts = urllib.parse.urlparse(systemId)
+        scheme, netloc, path, params, query, fragment = parts
+        # XXX should we check the scheme here as well?
+        if path and not path.endswith("/"):
+            path = posixpath.dirname(path) + "/"
+            parts = scheme, netloc, path, params, query, fragment
+            source.baseURI = urllib.parse.urlunparse(parts)
+
+        return source
+
+    def _get_opener(self):
+        try:
+            return self._opener
+        except AttributeError:
+            self._opener = self._create_opener()
+            return self._opener
+
+    def _create_opener(self):
+        import urllib.request
+        return urllib.request.build_opener()
+
+    def _guess_media_encoding(self, source):
+        info = source.byteStream.info()
+        if "Content-Type" in info:
+            for param in info.getplist():
+                if param.startswith("charset="):
+                    return param.split("=", 1)[1].lower()
+
+
+class DOMInputSource(object):
+    __slots__ = ('byteStream', 'characterStream', 'stringData',
+                 'encoding', 'publicId', 'systemId', 'baseURI')
+
+    def __init__(self):
+        self.byteStream = None
+        self.characterStream = None
+        self.stringData = None
+        self.encoding = None
+        self.publicId = None
+        self.systemId = None
+        self.baseURI = None
+
+    def _get_byteStream(self):
+        return self.byteStream
+    def _set_byteStream(self, byteStream):
+        self.byteStream = byteStream
+
+    def _get_characterStream(self):
+        return self.characterStream
+    def _set_characterStream(self, characterStream):
+        self.characterStream = characterStream
+
+    def _get_stringData(self):
+        return self.stringData
+    def _set_stringData(self, data):
+        self.stringData = data
+
+    def _get_encoding(self):
+        return self.encoding
+    def _set_encoding(self, encoding):
+        self.encoding = encoding
+
+    def _get_publicId(self):
+        return self.publicId
+    def _set_publicId(self, publicId):
+        self.publicId = publicId
+
+    def _get_systemId(self):
+        return self.systemId
+    def _set_systemId(self, systemId):
+        self.systemId = systemId
+
+    def _get_baseURI(self):
+        return self.baseURI
+    def _set_baseURI(self, uri):
+        self.baseURI = uri
+
+
+class DOMBuilderFilter:
+    """Element filter which can be used to tailor construction of
+    a DOM instance.
+    """
+
+    # There's really no need for this class; concrete implementations
+    # should just implement the endElement() and startElement()
+    # methods as appropriate.  Using this makes it easy to only
+    # implement one of them.
+
+    FILTER_ACCEPT = 1
+    FILTER_REJECT = 2
+    FILTER_SKIP = 3
+    FILTER_INTERRUPT = 4
+
+    whatToShow = NodeFilter.SHOW_ALL
+
+    def _get_whatToShow(self):
+        return self.whatToShow
+
+    def acceptNode(self, element):
+        return self.FILTER_ACCEPT
+
+    def startContainer(self, element):
+        return self.FILTER_ACCEPT
+
+del NodeFilter
+
+
+class _AsyncDeprecatedProperty:
+    def warn(self, cls):
+        clsname = cls.__name__
+        warnings.warn(
+            "{cls}.async is deprecated; use {cls}.async_".format(cls=clsname),
+            DeprecationWarning)
+
+    def __get__(self, instance, cls):
+        self.warn(cls)
+        if instance is not None:
+            return instance.async_
+        return False
+
+    def __set__(self, instance, value):
+        self.warn(type(instance))
+        setattr(instance, 'async_', value)
+
+
+class DocumentLS:
+    """Mixin to create documents that conform to the load/save spec."""
+
+    async_ = False
+    locals()['async'] = _AsyncDeprecatedProperty()  # Avoid DeprecationWarning
+
+    def _get_async(self):
+        return False
+
+    def _set_async(self, flag):
+        if flag:
+            raise xml.dom.NotSupportedErr(
+                "asynchronous document loading is not supported")
+
+    def abort(self):
+        # What does it mean to "clear" a document?  Does the
+        # documentElement disappear?
+        raise NotImplementedError(
+            "haven't figured out what this means yet")
+
+    def load(self, uri):
+        raise NotImplementedError("haven't written this yet")
+
+    def loadXML(self, source):
+        raise NotImplementedError("haven't written this yet")
+
+    def saveXML(self, snode):
+        if snode is None:
+            snode = self
+        elif snode.ownerDocument is not self:
+            raise xml.dom.WrongDocumentErr()
+        return snode.toxml()
+
+
+del _AsyncDeprecatedProperty
+
+
+class DOMImplementationLS:
+    MODE_SYNCHRONOUS = 1
+    MODE_ASYNCHRONOUS = 2
+
+    def createDOMBuilder(self, mode, schemaType):
+        if schemaType is not None:
+            raise xml.dom.NotSupportedErr(
+                "schemaType not yet supported")
+        if mode == self.MODE_SYNCHRONOUS:
+            return DOMBuilder()
+        if mode == self.MODE_ASYNCHRONOUS:
+            raise xml.dom.NotSupportedErr(
+                "asynchronous builders are not supported")
+        raise ValueError("unknown value for mode")
+
+    def createDOMWriter(self):
+        raise NotImplementedError(
+            "the writer interface hasn't been written yet!")
+
+    def createDOMInputSource(self):
+        return DOMInputSource()
diff --git a/Lib/xml/etree/ElementInclude.py b/Lib/xml/etree/ElementInclude.py
new file mode 100644
index 000000000..963470e3b
--- /dev/null
+++ b/Lib/xml/etree/ElementInclude.py
@@ -0,0 +1,143 @@
+#
+# ElementTree
+# $Id: ElementInclude.py 3375 2008-02-13 08:05:08Z fredrik $
+#
+# limited xinclude support for element trees
+#
+# history:
+# 2003-08-15 fl   created
+# 2003-11-14 fl   fixed default loader
+#
+# Copyright (c) 2003-2004 by Fredrik Lundh.  All rights reserved.
+#
+# fredrik@pythonware.com
+# http://www.pythonware.com
+#
+# --------------------------------------------------------------------
+# The ElementTree toolkit is
+#
+# Copyright (c) 1999-2008 by Fredrik Lundh
+#
+# By obtaining, using, and/or copying this software and/or its
+# associated documentation, you agree that you have read, understood,
+# and will comply with the following terms and conditions:
+#
+# Permission to use, copy, modify, and distribute this software and
+# its associated documentation for any purpose and without fee is
+# hereby granted, provided that the above copyright notice appears in
+# all copies, and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of
+# Secret Labs AB or the author not be used in advertising or publicity
+# pertaining to distribution of the software without specific, written
+# prior permission.
+#
+# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
+# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
+# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+# --------------------------------------------------------------------
+
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/psf/license for licensing details.
+
+##
+# Limited XInclude support for the ElementTree package.
+##
+
+import copy
+from . import ElementTree
+
+XINCLUDE = "{http://www.w3.org/2001/XInclude}"
+
+XINCLUDE_INCLUDE = XINCLUDE + "include"
+XINCLUDE_FALLBACK = XINCLUDE + "fallback"
+
+##
+# Fatal include error.
+
+class FatalIncludeError(SyntaxError):
+    pass
+
+##
+# Default loader.  This loader reads an included resource from disk.
+#
+# @param href Resource reference.
+# @param parse Parse mode.  Either "xml" or "text".
+# @param encoding Optional text encoding (UTF-8 by default for "text").
+# @return The expanded resource.  If the parse mode is "xml", this
+#    is an ElementTree instance.  If the parse mode is "text", this
+#    is a Unicode string.  If the loader fails, it can return None
+#    or raise an OSError exception.
+# @throws OSError If the loader fails to load the resource.
+
+def default_loader(href, parse, encoding=None):
+    if parse == "xml":
+        with open(href, 'rb') as file:
+            data = ElementTree.parse(file).getroot()
+    else:
+        if not encoding:
+            encoding = 'UTF-8'
+        with open(href, 'r', encoding=encoding) as file:
+            data = file.read()
+    return data
+
+##
+# Expand XInclude directives.
+#
+# @param elem Root element.
+# @param loader Optional resource loader.  If omitted, it defaults
+#     to {@link default_loader}.  If given, it should be a callable
+#     that implements the same interface as <b>default_loader</b>.
+# @throws FatalIncludeError If the function fails to include a given
+#     resource, or if the tree contains malformed XInclude elements.
+# @throws OSError If the function fails to load a given resource.
+
+def include(elem, loader=None):
+    if loader is None:
+        loader = default_loader
+    # look for xinclude elements
+    i = 0
+    while i < len(elem):
+        e = elem[i]
+        if e.tag == XINCLUDE_INCLUDE:
+            # process xinclude directive
+            href = e.get("href")
+            parse = e.get("parse", "xml")
+            if parse == "xml":
+                node = loader(href, parse)
+                if node is None:
+                    raise FatalIncludeError(
+                        "cannot load %r as %r" % (href, parse)
+                        )
+                node = copy.copy(node)
+                if e.tail:
+                    node.tail = (node.tail or "") + e.tail
+                elem[i] = node
+            elif parse == "text":
+                text = loader(href, parse, e.get("encoding"))
+                if text is None:
+                    raise FatalIncludeError(
+                        "cannot load %r as %r" % (href, parse)
+                        )
+                if i:
+                    node = elem[i-1]
+                    node.tail = (node.tail or "") + text + (e.tail or "")
+                else:
+                    elem.text = (elem.text or "") + text + (e.tail or "")
+                del elem[i]
+                continue
+            else:
+                raise FatalIncludeError(
+                    "unknown parse type in xi:include tag (%r)" % parse
+                )
+        elif e.tag == XINCLUDE_FALLBACK:
+            raise FatalIncludeError(
+                "xi:fallback tag must be child of xi:include (%r)" % e.tag
+                )
+        else:
+            include(e, loader)
+        i = i + 1
diff --git a/Lib/xml/etree/ElementPath.py b/Lib/xml/etree/ElementPath.py
new file mode 100644
index 000000000..ab6b79a77
--- /dev/null
+++ b/Lib/xml/etree/ElementPath.py
@@ -0,0 +1,314 @@
+#
+# ElementTree
+# $Id: ElementPath.py 3375 2008-02-13 08:05:08Z fredrik $
+#
+# limited xpath support for element trees
+#
+# history:
+# 2003-05-23 fl   created
+# 2003-05-28 fl   added support for // etc
+# 2003-08-27 fl   fixed parsing of periods in element names
+# 2007-09-10 fl   new selection engine
+# 2007-09-12 fl   fixed parent selector
+# 2007-09-13 fl   added iterfind; changed findall to return a list
+# 2007-11-30 fl   added namespaces support
+# 2009-10-30 fl   added child element value filter
+#
+# Copyright (c) 2003-2009 by Fredrik Lundh.  All rights reserved.
+#
+# fredrik@pythonware.com
+# http://www.pythonware.com
+#
+# --------------------------------------------------------------------
+# The ElementTree toolkit is
+#
+# Copyright (c) 1999-2009 by Fredrik Lundh
+#
+# By obtaining, using, and/or copying this software and/or its
+# associated documentation, you agree that you have read, understood,
+# and will comply with the following terms and conditions:
+#
+# Permission to use, copy, modify, and distribute this software and
+# its associated documentation for any purpose and without fee is
+# hereby granted, provided that the above copyright notice appears in
+# all copies, and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of
+# Secret Labs AB or the author not be used in advertising or publicity
+# pertaining to distribution of the software without specific, written
+# prior permission.
+#
+# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
+# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
+# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+# --------------------------------------------------------------------
+
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/psf/license for licensing details.
+
+##
+# Implementation module for XPath support.  There's usually no reason
+# to import this module directly; the <b>ElementTree</b> does this for
+# you, if needed.
+##
+
+import re
+
+xpath_tokenizer_re = re.compile(
+    r"("
+    r"'[^']*'|\"[^\"]*\"|"
+    r"::|"
+    r"//?|"
+    r"\.\.|"
+    r"\(\)|"
+    r"[/.*:\[\]\(\)@=])|"
+    r"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|"
+    r"\s+"
+    )
+
+def xpath_tokenizer(pattern, namespaces=None):
+    for token in xpath_tokenizer_re.findall(pattern):
+        tag = token[1]
+        if tag and tag[0] != "{" and ":" in tag:
+            try:
+                prefix, uri = tag.split(":", 1)
+                if not namespaces:
+                    raise KeyError
+                yield token[0], "{%s}%s" % (namespaces[prefix], uri)
+            except KeyError:
+                raise SyntaxError("prefix %r not found in prefix map" % prefix)
+        else:
+            yield token
+
+def get_parent_map(context):
+    parent_map = context.parent_map
+    if parent_map is None:
+        context.parent_map = parent_map = {}
+        for p in context.root.iter():
+            for e in p:
+                parent_map[e] = p
+    return parent_map
+
+def prepare_child(next, token):
+    tag = token[1]
+    def select(context, result):
+        for elem in result:
+            for e in elem:
+                if e.tag == tag:
+                    yield e
+    return select
+
+def prepare_star(next, token):
+    def select(context, result):
+        for elem in result:
+            yield from elem
+    return select
+
+def prepare_self(next, token):
+    def select(context, result):
+        yield from result
+    return select
+
+def prepare_descendant(next, token):
+    try:
+        token = next()
+    except StopIteration:
+        return
+    if token[0] == "*":
+        tag = "*"
+    elif not token[0]:
+        tag = token[1]
+    else:
+        raise SyntaxError("invalid descendant")
+    def select(context, result):
+        for elem in result:
+            for e in elem.iter(tag):
+                if e is not elem:
+                    yield e
+    return select
+
+def prepare_parent(next, token):
+    def select(context, result):
+        # FIXME: raise error if .. is applied at toplevel?
+        parent_map = get_parent_map(context)
+        result_map = {}
+        for elem in result:
+            if elem in parent_map:
+                parent = parent_map[elem]
+                if parent not in result_map:
+                    result_map[parent] = None
+                    yield parent
+    return select
+
+def prepare_predicate(next, token):
+    # FIXME: replace with real parser!!! refs:
+    # http://effbot.org/zone/simple-iterator-parser.htm
+    # http://javascript.crockford.com/tdop/tdop.html
+    signature = []
+    predicate = []
+    while 1:
+        try:
+            token = next()
+        except StopIteration:
+            return
+        if token[0] == "]":
+            break
+        if token[0] and token[0][:1] in "'\"":
+            token = "'", token[0][1:-1]
+        signature.append(token[0] or "-")
+        predicate.append(token[1])
+    signature = "".join(signature)
+    # use signature to determine predicate type
+    if signature == "@-":
+        # [@attribute] predicate
+        key = predicate[1]
+        def select(context, result):
+            for elem in result:
+                if elem.get(key) is not None:
+                    yield elem
+        return select
+    if signature == "@-='":
+        # [@attribute='value']
+        key = predicate[1]
+        value = predicate[-1]
+        def select(context, result):
+            for elem in result:
+                if elem.get(key) == value:
+                    yield elem
+        return select
+    if signature == "-" and not re.match(r"\-?\d+$", predicate[0]):
+        # [tag]
+        tag = predicate[0]
+        def select(context, result):
+            for elem in result:
+                if elem.find(tag) is not None:
+                    yield elem
+        return select
+    if signature == "-='" and not re.match(r"\-?\d+$", predicate[0]):
+        # [tag='value']
+        tag = predicate[0]
+        value = predicate[-1]
+        def select(context, result):
+            for elem in result:
+                for e in elem.findall(tag):
+                    if "".join(e.itertext()) == value:
+                        yield elem
+                        break
+        return select
+    if signature == "-" or signature == "-()" or signature == "-()-":
+        # [index] or [last()] or [last()-index]
+        if signature == "-":
+            # [index]
+            index = int(predicate[0]) - 1
+            if index < 0:
+                raise SyntaxError("XPath position >= 1 expected")
+        else:
+            if predicate[0] != "last":
+                raise SyntaxError("unsupported function")
+            if signature == "-()-":
+                try:
+                    index = int(predicate[2]) - 1
+                except ValueError:
+                    raise SyntaxError("unsupported expression")
+                if index > -2:
+                    raise SyntaxError("XPath offset from last() must be negative")
+            else:
+                index = -1
+        def select(context, result):
+            parent_map = get_parent_map(context)
+            for elem in result:
+                try:
+                    parent = parent_map[elem]
+                    # FIXME: what if the selector is "*" ?
+                    elems = list(parent.findall(elem.tag))
+                    if elems[index] is elem:
+                        yield elem
+                except (IndexError, KeyError):
+                    pass
+        return select
+    raise SyntaxError("invalid predicate")
+
+ops = {
+    "": prepare_child,
+    "*": prepare_star,
+    ".": prepare_self,
+    "..": prepare_parent,
+    "//": prepare_descendant,
+    "[": prepare_predicate,
+    }
+
+_cache = {}
+
+class _SelectorContext:
+    parent_map = None
+    def __init__(self, root):
+        self.root = root
+
+# --------------------------------------------------------------------
+
+##
+# Generate all matching objects.
+
+def iterfind(elem, path, namespaces=None):
+    # compile selector pattern
+    cache_key = (path, None if namespaces is None
+                            else tuple(sorted(namespaces.items())))
+    if path[-1:] == "/":
+        path = path + "*" # implicit all (FIXME: keep this?)
+    try:
+        selector = _cache[cache_key]
+    except KeyError:
+        if len(_cache) > 100:
+            _cache.clear()
+        if path[:1] == "/":
+            raise SyntaxError("cannot use absolute path on element")
+        next = iter(xpath_tokenizer(path, namespaces)).__next__
+        try:
+            token = next()
+        except StopIteration:
+            return
+        selector = []
+        while 1:
+            try:
+                selector.append(ops[token[0]](next, token))
+            except StopIteration:
+                raise SyntaxError("invalid path")
+            try:
+                token = next()
+                if token[0] == "/":
+                    token = next()
+            except StopIteration:
+                break
+        _cache[cache_key] = selector
+    # execute selector pattern
+    result = [elem]
+    context = _SelectorContext(elem)
+    for select in selector:
+        result = select(context, result)
+    return result
+
+##
+# Find first matching object.
+
+def find(elem, path, namespaces=None):
+    return next(iterfind(elem, path, namespaces), None)
+
+##
+# Find all matching objects.
+
+def findall(elem, path, namespaces=None):
+    return list(iterfind(elem, path, namespaces))
+
+##
+# Find text for first matching object.
+
+def findtext(elem, path, default=None, namespaces=None):
+    try:
+        elem = next(iterfind(elem, path, namespaces))
+        return elem.text or ""
+    except StopIteration:
+        return default
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
new file mode 100644
index 000000000..cf4e1da97
--- /dev/null
+++ b/Lib/xml/etree/ElementTree.py
@@ -0,0 +1,1656 @@
+"""Lightweight XML support for Python.
+
+ XML is an inherently hierarchical data format, and the most natural way to
+ represent it is with a tree.  This module has two classes for this purpose:
+
+    1. ElementTree represents the whole XML document as a tree and
+
+    2. Element represents a single node in this tree.
+
+ Interactions with the whole document (reading and writing to/from files) are
+ usually done on the ElementTree level.  Interactions with a single XML element
+ and its sub-elements are done on the Element level.
+
+ Element is a flexible container object designed to store hierarchical data
+ structures in memory. It can be described as a cross between a list and a
+ dictionary.  Each Element has a number of properties associated with it:
+
+    'tag' - a string containing the element's name.
+
+    'attributes' - a Python dictionary storing the element's attributes.
+
+    'text' - a string containing the element's text content.
+
+    'tail' - an optional string containing text after the element's end tag.
+
+    And a number of child elements stored in a Python sequence.
+
+ To create an element instance, use the Element constructor,
+ or the SubElement factory function.
+
+ You can also use the ElementTree class to wrap an element structure
+ and convert it to and from XML.
+
+"""
+
+#---------------------------------------------------------------------
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/psf/license for licensing details.
+#
+# ElementTree
+# Copyright (c) 1999-2008 by Fredrik Lundh.  All rights reserved.
+#
+# fredrik@pythonware.com
+# http://www.pythonware.com
+# --------------------------------------------------------------------
+# The ElementTree toolkit is
+#
+# Copyright (c) 1999-2008 by Fredrik Lundh
+#
+# By obtaining, using, and/or copying this software and/or its
+# associated documentation, you agree that you have read, understood,
+# and will comply with the following terms and conditions:
+#
+# Permission to use, copy, modify, and distribute this software and
+# its associated documentation for any purpose and without fee is
+# hereby granted, provided that the above copyright notice appears in
+# all copies, and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of
+# Secret Labs AB or the author not be used in advertising or publicity
+# pertaining to distribution of the software without specific, written
+# prior permission.
+#
+# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
+# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
+# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+# --------------------------------------------------------------------
+
+__all__ = [
+    # public symbols
+    "Comment",
+    "dump",
+    "Element", "ElementTree",
+    "fromstring", "fromstringlist",
+    "iselement", "iterparse",
+    "parse", "ParseError",
+    "PI", "ProcessingInstruction",
+    "QName",
+    "SubElement",
+    "tostring", "tostringlist",
+    "TreeBuilder",
+    "VERSION",
+    "XML", "XMLID",
+    "XMLParser", "XMLPullParser",
+    "register_namespace",
+    ]
+
+VERSION = "1.3.0"
+
+import sys
+import re
+import warnings
+import io
+import collections
+import contextlib
+
+from . import ElementPath
+
+
+class ParseError(SyntaxError):
+    """An error when parsing an XML document.
+
+    In addition to its exception value, a ParseError contains
+    two extra attributes:
+        'code'     - the specific exception code
+        'position' - the line and column of the error
+
+    """
+    pass
+
+# --------------------------------------------------------------------
+
+
+def iselement(element):
+    """Return True if *element* appears to be an Element."""
+    return hasattr(element, 'tag')
+
+
+class Element:
+    """An XML element.
+
+    This class is the reference implementation of the Element interface.
+
+    An element's length is its number of subelements.  That means if you
+    want to check if an element is truly empty, you should check BOTH
+    its length AND its text attribute.
+
+    The element tag, attribute names, and attribute values can be either
+    bytes or strings.
+
+    *tag* is the element name.  *attrib* is an optional dictionary containing
+    element attributes. *extra* are additional element attributes given as
+    keyword arguments.
+
+    Example form:
+        <tag attrib>text<child/>...</tag>tail
+
+    """
+
+    tag = None
+    """The element's name."""
+
+    attrib = None
+    """Dictionary of the element's attributes."""
+
+    text = None
+    """
+    Text before first subelement. This is either a string or the value None.
+    Note that if there is no text, this attribute may be either
+    None or the empty string, depending on the parser.
+
+    """
+
+    tail = None
+    """
+    Text after this element's end tag, but before the next sibling element's
+    start tag.  This is either a string or the value None.  Note that if there
+    was no text, this attribute may be either None or an empty string,
+    depending on the parser.
+
+    """
+
+    def __init__(self, tag, attrib={}, **extra):
+        if not isinstance(attrib, dict):
+            raise TypeError("attrib must be dict, not %s" % (
+                attrib.__class__.__name__,))
+        attrib = attrib.copy()
+        attrib.update(extra)
+        self.tag = tag
+        self.attrib = attrib
+        self._children = []
+
+    def __repr__(self):
+        return "<%s %r at %#x>" % (self.__class__.__name__, self.tag, id(self))
+
+    def makeelement(self, tag, attrib):
+        """Create a new element with the same type.
+
+        *tag* is a string containing the element name.
+        *attrib* is a dictionary containing the element attributes.
+
+        Do not call this method, use the SubElement factory function instead.
+
+        """
+        return self.__class__(tag, attrib)
+
+    def copy(self):
+        """Return copy of current element.
+
+        This creates a shallow copy. Subelements will be shared with the
+        original tree.
+
+        """
+        elem = self.makeelement(self.tag, self.attrib)
+        elem.text = self.text
+        elem.tail = self.tail
+        elem[:] = self
+        return elem
+
+    def __len__(self):
+        return len(self._children)
+
+    def __bool__(self):
+        warnings.warn(
+            "The behavior of this method will change in future versions.  "
+            "Use specific 'len(elem)' or 'elem is not None' test instead.",
+            FutureWarning, stacklevel=2
+            )
+        return len(self._children) != 0 # emulate old behaviour, for now
+
+    def __getitem__(self, index):
+        return self._children[index]
+
+    def __setitem__(self, index, element):
+        # if isinstance(index, slice):
+        #     for elt in element:
+        #         assert iselement(elt)
+        # else:
+        #     assert iselement(element)
+        self._children[index] = element
+
+    def __delitem__(self, index):
+        del self._children[index]
+
+    def append(self, subelement):
+        """Add *subelement* to the end of this element.
+
+        The new element will appear in document order after the last existing
+        subelement (or directly after the text, if it's the first subelement),
+        but before the end tag for this element.
+
+        """
+        self._assert_is_element(subelement)
+        self._children.append(subelement)
+
+    def extend(self, elements):
+        """Append subelements from a sequence.
+
+        *elements* is a sequence with zero or more elements.
+
+        """
+        for element in elements:
+            self._assert_is_element(element)
+        self._children.extend(elements)
+
+    def insert(self, index, subelement):
+        """Insert *subelement* at position *index*."""
+        self._assert_is_element(subelement)
+        self._children.insert(index, subelement)
+
+    def _assert_is_element(self, e):
+        # Need to refer to the actual Python implementation, not the
+        # shadowing C implementation.
+        if not isinstance(e, _Element_Py):
+            raise TypeError('expected an Element, not %s' % type(e).__name__)
+
+    def remove(self, subelement):
+        """Remove matching subelement.
+
+        Unlike the find methods, this method compares elements based on
+        identity, NOT ON tag value or contents.  To remove subelements by
+        other means, the easiest way is to use a list comprehension to
+        select what elements to keep, and then use slice assignment to update
+        the parent element.
+
+        ValueError is raised if a matching element could not be found.
+
+        """
+        # assert iselement(element)
+        self._children.remove(subelement)
+
+    def getchildren(self):
+        """(Deprecated) Return all subelements.
+
+        Elements are returned in document order.
+
+        """
+        warnings.warn(
+            "This method will be removed in future versions.  "
+            "Use 'list(elem)' or iteration over elem instead.",
+            DeprecationWarning, stacklevel=2
+            )
+        return self._children
+
+    def find(self, path, namespaces=None):
+        """Find first matching element by tag name or path.
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return the first matching element, or None if no element was found.
+
+        """
+        return ElementPath.find(self, path, namespaces)
+
+    def findtext(self, path, default=None, namespaces=None):
+        """Find text for first matching element by tag name or path.
+
+        *path* is a string having either an element tag or an XPath,
+        *default* is the value to return if the element was not found,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return text content of first matching element, or default value if
+        none was found.  Note that if an element is found having no text
+        content, the empty string is returned.
+
+        """
+        return ElementPath.findtext(self, path, default, namespaces)
+
+    def findall(self, path, namespaces=None):
+        """Find all matching subelements by tag name or path.
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Returns list containing all matching elements in document order.
+
+        """
+        return ElementPath.findall(self, path, namespaces)
+
+    def iterfind(self, path, namespaces=None):
+        """Find all matching subelements by tag name or path.
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return an iterable yielding all matching elements in document order.
+
+        """
+        return ElementPath.iterfind(self, path, namespaces)
+
+    def clear(self):
+        """Reset element.
+
+        This function removes all subelements, clears all attributes, and sets
+        the text and tail attributes to None.
+
+        """
+        self.attrib.clear()
+        self._children = []
+        self.text = self.tail = None
+
+    def get(self, key, default=None):
+        """Get element attribute.
+
+        Equivalent to attrib.get, but some implementations may handle this a
+        bit more efficiently.  *key* is what attribute to look for, and
+        *default* is what to return if the attribute was not found.
+
+        Returns a string containing the attribute value, or the default if
+        attribute was not found.
+
+        """
+        return self.attrib.get(key, default)
+
+    def set(self, key, value):
+        """Set element attribute.
+
+        Equivalent to attrib[key] = value, but some implementations may handle
+        this a bit more efficiently.  *key* is what attribute to set, and
+        *value* is the attribute value to set it to.
+
+        """
+        self.attrib[key] = value
+
+    def keys(self):
+        """Get list of attribute names.
+
+        Names are returned in an arbitrary order, just like an ordinary
+        Python dict.  Equivalent to attrib.keys()
+
+        """
+        return self.attrib.keys()
+
+    def items(self):
+        """Get element attributes as a sequence.
+
+        The attributes are returned in arbitrary order.  Equivalent to
+        attrib.items().
+
+        Return a list of (name, value) tuples.
+
+        """
+        return self.attrib.items()
+
+    def iter(self, tag=None):
+        """Create tree iterator.
+
+        The iterator loops over the element and all subelements in document
+        order, returning all elements with a matching tag.
+
+        If the tree structure is modified during iteration, new or removed
+        elements may or may not be included.  To get a stable set, use the
+        list() function on the iterator, and loop over the resulting list.
+
+        *tag* is what tags to look for (default is to return all elements)
+
+        Return an iterator containing all the matching elements.
+
+        """
+        if tag == "*":
+            tag = None
+        if tag is None or self.tag == tag:
+            yield self
+        for e in self._children:
+            yield from e.iter(tag)
+
+    # compatibility
+    def getiterator(self, tag=None):
+        # Change for a DeprecationWarning in 1.4
+        warnings.warn(
+            "This method will be removed in future versions.  "
+            "Use 'elem.iter()' or 'list(elem.iter())' instead.",
+            PendingDeprecationWarning, stacklevel=2
+        )
+        return list(self.iter(tag))
+
+    def itertext(self):
+        """Create text iterator.
+
+        The iterator loops over the element and all subelements in document
+        order, returning all inner text.
+
+        """
+        tag = self.tag
+        if not isinstance(tag, str) and tag is not None:
+            return
+        t = self.text
+        if t:
+            yield t
+        for e in self:
+            yield from e.itertext()
+            t = e.tail
+            if t:
+                yield t
+
+
+def SubElement(parent, tag, attrib={}, **extra):
+    """Subelement factory which creates an element instance, and appends it
+    to an existing parent.
+
+    The element tag, attribute names, and attribute values can be either
+    bytes or Unicode strings.
+
+    *parent* is the parent element, *tag* is the subelements name, *attrib* is
+    an optional directory containing element attributes, *extra* are
+    additional attributes given as keyword arguments.
+
+    """
+    attrib = attrib.copy()
+    attrib.update(extra)
+    element = parent.makeelement(tag, attrib)
+    parent.append(element)
+    return element
+
+
+def Comment(text=None):
+    """Comment element factory.
+
+    This function creates a special element which the standard serializer
+    serializes as an XML comment.
+
+    *text* is a string containing the comment string.
+
+    """
+    element = Element(Comment)
+    element.text = text
+    return element
+
+
+def ProcessingInstruction(target, text=None):
+    """Processing Instruction element factory.
+
+    This function creates a special element which the standard serializer
+    serializes as an XML comment.
+
+    *target* is a string containing the processing instruction, *text* is a
+    string containing the processing instruction contents, if any.
+
+    """
+    element = Element(ProcessingInstruction)
+    element.text = target
+    if text:
+        element.text = element.text + " " + text
+    return element
+
+PI = ProcessingInstruction
+
+
+class QName:
+    """Qualified name wrapper.
+
+    This class can be used to wrap a QName attribute value in order to get
+    proper namespace handing on output.
+
+    *text_or_uri* is a string containing the QName value either in the form
+    {uri}local, or if the tag argument is given, the URI part of a QName.
+
+    *tag* is an optional argument which if given, will make the first
+    argument (text_or_uri) be interpreted as a URI, and this argument (tag)
+    be interpreted as a local name.
+
+    """
+    def __init__(self, text_or_uri, tag=None):
+        if tag:
+            text_or_uri = "{%s}%s" % (text_or_uri, tag)
+        self.text = text_or_uri
+    def __str__(self):
+        return self.text
+    def __repr__(self):
+        return '<%s %r>' % (self.__class__.__name__, self.text)
+    def __hash__(self):
+        return hash(self.text)
+    def __le__(self, other):
+        if isinstance(other, QName):
+            return self.text <= other.text
+        return self.text <= other
+    def __lt__(self, other):
+        if isinstance(other, QName):
+            return self.text < other.text
+        return self.text < other
+    def __ge__(self, other):
+        if isinstance(other, QName):
+            return self.text >= other.text
+        return self.text >= other
+    def __gt__(self, other):
+        if isinstance(other, QName):
+            return self.text > other.text
+        return self.text > other
+    def __eq__(self, other):
+        if isinstance(other, QName):
+            return self.text == other.text
+        return self.text == other
+
+# --------------------------------------------------------------------
+
+
+class ElementTree:
+    """An XML element hierarchy.
+
+    This class also provides support for serialization to and from
+    standard XML.
+
+    *element* is an optional root element node,
+    *file* is an optional file handle or file name of an XML file whose
+    contents will be used to initialize the tree with.
+
+    """
+    def __init__(self, element=None, file=None):
+        # assert element is None or iselement(element)
+        self._root = element # first node
+        if file:
+            self.parse(file)
+
+    def getroot(self):
+        """Return root element of this tree."""
+        return self._root
+
+    def _setroot(self, element):
+        """Replace root element of this tree.
+
+        This will discard the current contents of the tree and replace it
+        with the given element.  Use with care!
+
+        """
+        # assert iselement(element)
+        self._root = element
+
+    def parse(self, source, parser=None):
+        """Load external XML document into element tree.
+
+        *source* is a file name or file object, *parser* is an optional parser
+        instance that defaults to XMLParser.
+
+        ParseError is raised if the parser fails to parse the document.
+
+        Returns the root element of the given source document.
+
+        """
+        close_source = False
+        if not hasattr(source, "read"):
+            source = open(source, "rb")
+            close_source = True
+        try:
+            if parser is None:
+                # If no parser was specified, create a default XMLParser
+                parser = XMLParser()
+                if hasattr(parser, '_parse_whole'):
+                    # The default XMLParser, when it comes from an accelerator,
+                    # can define an internal _parse_whole API for efficiency.
+                    # It can be used to parse the whole source without feeding
+                    # it with chunks.
+                    self._root = parser._parse_whole(source)
+                    return self._root
+            while True:
+                data = source.read(65536)
+                if not data:
+                    break
+                parser.feed(data)
+            self._root = parser.close()
+            return self._root
+        finally:
+            if close_source:
+                source.close()
+
+    def iter(self, tag=None):
+        """Create and return tree iterator for the root element.
+
+        The iterator loops over all elements in this tree, in document order.
+
+        *tag* is a string with the tag name to iterate over
+        (default is to return all elements).
+
+        """
+        # assert self._root is not None
+        return self._root.iter(tag)
+
+    # compatibility
+    def getiterator(self, tag=None):
+        # Change for a DeprecationWarning in 1.4
+        warnings.warn(
+            "This method will be removed in future versions.  "
+            "Use 'tree.iter()' or 'list(tree.iter())' instead.",
+            PendingDeprecationWarning, stacklevel=2
+        )
+        return list(self.iter(tag))
+
+    def find(self, path, namespaces=None):
+        """Find first matching element by tag name or path.
+
+        Same as getroot().find(path), which is Element.find()
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return the first matching element, or None if no element was found.
+
+        """
+        # assert self._root is not None
+        if path[:1] == "/":
+            path = "." + path
+            warnings.warn(
+                "This search is broken in 1.3 and earlier, and will be "
+                "fixed in a future version.  If you rely on the current "
+                "behaviour, change it to %r" % path,
+                FutureWarning, stacklevel=2
+                )
+        return self._root.find(path, namespaces)
+
+    def findtext(self, path, default=None, namespaces=None):
+        """Find first matching element by tag name or path.
+
+        Same as getroot().findtext(path),  which is Element.findtext()
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return the first matching element, or None if no element was found.
+
+        """
+        # assert self._root is not None
+        if path[:1] == "/":
+            path = "." + path
+            warnings.warn(
+                "This search is broken in 1.3 and earlier, and will be "
+                "fixed in a future version.  If you rely on the current "
+                "behaviour, change it to %r" % path,
+                FutureWarning, stacklevel=2
+                )
+        return self._root.findtext(path, default, namespaces)
+
+    def findall(self, path, namespaces=None):
+        """Find all matching subelements by tag name or path.
+
+        Same as getroot().findall(path), which is Element.findall().
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return list containing all matching elements in document order.
+
+        """
+        # assert self._root is not None
+        if path[:1] == "/":
+            path = "." + path
+            warnings.warn(
+                "This search is broken in 1.3 and earlier, and will be "
+                "fixed in a future version.  If you rely on the current "
+                "behaviour, change it to %r" % path,
+                FutureWarning, stacklevel=2
+                )
+        return self._root.findall(path, namespaces)
+
+    def iterfind(self, path, namespaces=None):
+        """Find all matching subelements by tag name or path.
+
+        Same as getroot().iterfind(path), which is element.iterfind()
+
+        *path* is a string having either an element tag or an XPath,
+        *namespaces* is an optional mapping from namespace prefix to full name.
+
+        Return an iterable yielding all matching elements in document order.
+
+        """
+        # assert self._root is not None
+        if path[:1] == "/":
+            path = "." + path
+            warnings.warn(
+                "This search is broken in 1.3 and earlier, and will be "
+                "fixed in a future version.  If you rely on the current "
+                "behaviour, change it to %r" % path,
+                FutureWarning, stacklevel=2
+                )
+        return self._root.iterfind(path, namespaces)
+
+    def write(self, file_or_filename,
+              encoding=None,
+              xml_declaration=None,
+              default_namespace=None,
+              method=None, *,
+              short_empty_elements=True):
+        """Write element tree to a file as XML.
+
+        Arguments:
+          *file_or_filename* -- file name or a file object opened for writing
+
+          *encoding* -- the output encoding (default: US-ASCII)
+
+          *xml_declaration* -- bool indicating if an XML declaration should be
+                               added to the output. If None, an XML declaration
+                               is added if encoding IS NOT either of:
+                               US-ASCII, UTF-8, or Unicode
+
+          *default_namespace* -- sets the default XML namespace (for "xmlns")
+
+          *method* -- either "xml" (default), "html, "text", or "c14n"
+
+          *short_empty_elements* -- controls the formatting of elements
+                                    that contain no content. If True (default)
+                                    they are emitted as a single self-closed
+                                    tag, otherwise they are emitted as a pair
+                                    of start/end tags
+
+        """
+        if not method:
+            method = "xml"
+        elif method not in _serialize:
+            raise ValueError("unknown method %r" % method)
+        if not encoding:
+            if method == "c14n":
+                encoding = "utf-8"
+            else:
+                encoding = "us-ascii"
+        enc_lower = encoding.lower()
+        with _get_writer(file_or_filename, enc_lower) as write:
+            if method == "xml" and (xml_declaration or
+                    (xml_declaration is None and
+                     enc_lower not in ("utf-8", "us-ascii", "unicode"))):
+                declared_encoding = encoding
+                if enc_lower == "unicode":
+                    # Retrieve the default encoding for the xml declaration
+                    import locale
+                    declared_encoding = locale.getpreferredencoding()
+                write("<?xml version='1.0' encoding='%s'?>\n" % (
+                    declared_encoding,))
+            if method == "text":
+                _serialize_text(write, self._root)
+            else:
+                qnames, namespaces = _namespaces(self._root, default_namespace)
+                serialize = _serialize[method]
+                serialize(write, self._root, qnames, namespaces,
+                          short_empty_elements=short_empty_elements)
+
+    def write_c14n(self, file):
+        # lxml.etree compatibility.  use output method instead
+        return self.write(file, method="c14n")
+
+# --------------------------------------------------------------------
+# serialization support
+
+@contextlib.contextmanager
+def _get_writer(file_or_filename, encoding):
+    # returns text write method and release all resources after using
+    try:
+        write = file_or_filename.write
+    except AttributeError:
+        # file_or_filename is a file name
+        if encoding == "unicode":
+            file = open(file_or_filename, "w")
+        else:
+            file = open(file_or_filename, "w", encoding=encoding,
+                        errors="xmlcharrefreplace")
+        with file:
+            yield file.write
+    else:
+        # file_or_filename is a file-like object
+        # encoding determines if it is a text or binary writer
+        if encoding == "unicode":
+            # use a text writer as is
+            yield write
+        else:
+            # wrap a binary writer with TextIOWrapper
+            with contextlib.ExitStack() as stack:
+                if isinstance(file_or_filename, io.BufferedIOBase):
+                    file = file_or_filename
+                elif isinstance(file_or_filename, io.RawIOBase):
+                    file = io.BufferedWriter(file_or_filename)
+                    # Keep the original file open when the BufferedWriter is
+                    # destroyed
+                    stack.callback(file.detach)
+                else:
+                    # This is to handle passed objects that aren't in the
+                    # IOBase hierarchy, but just have a write method
+                    file = io.BufferedIOBase()
+                    file.writable = lambda: True
+                    file.write = write
+                    try:
+                        # TextIOWrapper uses this methods to determine
+                        # if BOM (for UTF-16, etc) should be added
+                        file.seekable = file_or_filename.seekable
+                        file.tell = file_or_filename.tell
+                    except AttributeError:
+                        pass
+                file = io.TextIOWrapper(file,
+                                        encoding=encoding,
+                                        errors="xmlcharrefreplace",
+                                        newline="\n")
+                # Keep the original file open when the TextIOWrapper is
+                # destroyed
+                stack.callback(file.detach)
+                yield file.write
+
+def _namespaces(elem, default_namespace=None):
+    # identify namespaces used in this tree
+
+    # maps qnames to *encoded* prefix:local names
+    qnames = {None: None}
+
+    # maps uri:s to prefixes
+    namespaces = {}
+    if default_namespace:
+        namespaces[default_namespace] = ""
+
+    def add_qname(qname):
+        # calculate serialized qname representation
+        try:
+            if qname[:1] == "{":
+                uri, tag = qname[1:].rsplit("}", 1)
+                prefix = namespaces.get(uri)
+                if prefix is None:
+                    prefix = _namespace_map.get(uri)
+                    if prefix is None:
+                        prefix = "ns%d" % len(namespaces)
+                    if prefix != "xml":
+                        namespaces[uri] = prefix
+                if prefix:
+                    qnames[qname] = "%s:%s" % (prefix, tag)
+                else:
+                    qnames[qname] = tag # default element
+            else:
+                if default_namespace:
+                    # FIXME: can this be handled in XML 1.0?
+                    raise ValueError(
+                        "cannot use non-qualified names with "
+                        "default_namespace option"
+                        )
+                qnames[qname] = qname
+        except TypeError:
+            _raise_serialization_error(qname)
+
+    # populate qname and namespaces table
+    for elem in elem.iter():
+        tag = elem.tag
+        if isinstance(tag, QName):
+            if tag.text not in qnames:
+                add_qname(tag.text)
+        elif isinstance(tag, str):
+            if tag not in qnames:
+                add_qname(tag)
+        elif tag is not None and tag is not Comment and tag is not PI:
+            _raise_serialization_error(tag)
+        for key, value in elem.items():
+            if isinstance(key, QName):
+                key = key.text
+            if key not in qnames:
+                add_qname(key)
+            if isinstance(value, QName) and value.text not in qnames:
+                add_qname(value.text)
+        text = elem.text
+        if isinstance(text, QName) and text.text not in qnames:
+            add_qname(text.text)
+    return qnames, namespaces
+
+def _serialize_xml(write, elem, qnames, namespaces,
+                   short_empty_elements, **kwargs):
+    tag = elem.tag
+    text = elem.text
+    if tag is Comment:
+        write("<!--%s-->" % text)
+    elif tag is ProcessingInstruction:
+        write("<?%s?>" % text)
+    else:
+        tag = qnames[tag]
+        if tag is None:
+            if text:
+                write(_escape_cdata(text))
+            for e in elem:
+                _serialize_xml(write, e, qnames, None,
+                               short_empty_elements=short_empty_elements)
+        else:
+            write("<" + tag)
+            items = list(elem.items())
+            if items or namespaces:
+                if namespaces:
+                    for v, k in sorted(namespaces.items(),
+                                       key=lambda x: x[1]):  # sort on prefix
+                        if k:
+                            k = ":" + k
+                        write(" xmlns%s=\"%s\"" % (
+                            k,
+                            _escape_attrib(v)
+                            ))
+                for k, v in sorted(items):  # lexical order
+                    if isinstance(k, QName):
+                        k = k.text
+                    if isinstance(v, QName):
+                        v = qnames[v.text]
+                    else:
+                        v = _escape_attrib(v)
+                    write(" %s=\"%s\"" % (qnames[k], v))
+            if text or len(elem) or not short_empty_elements:
+                write(">")
+                if text:
+                    write(_escape_cdata(text))
+                for e in elem:
+                    _serialize_xml(write, e, qnames, None,
+                                   short_empty_elements=short_empty_elements)
+                write("</" + tag + ">")
+            else:
+                write(" />")
+    if elem.tail:
+        write(_escape_cdata(elem.tail))
+
+HTML_EMPTY = ("area", "base", "basefont", "br", "col", "frame", "hr",
+              "img", "input", "isindex", "link", "meta", "param")
+
+try:
+    HTML_EMPTY = set(HTML_EMPTY)
+except NameError:
+    pass
+
+def _serialize_html(write, elem, qnames, namespaces, **kwargs):
+    tag = elem.tag
+    text = elem.text
+    if tag is Comment:
+        write("<!--%s-->" % _escape_cdata(text))
+    elif tag is ProcessingInstruction:
+        write("<?%s?>" % _escape_cdata(text))
+    else:
+        tag = qnames[tag]
+        if tag is None:
+            if text:
+                write(_escape_cdata(text))
+            for e in elem:
+                _serialize_html(write, e, qnames, None)
+        else:
+            write("<" + tag)
+            items = list(elem.items())
+            if items or namespaces:
+                if namespaces:
+                    for v, k in sorted(namespaces.items(),
+                                       key=lambda x: x[1]):  # sort on prefix
+                        if k:
+                            k = ":" + k
+                        write(" xmlns%s=\"%s\"" % (
+                            k,
+                            _escape_attrib(v)
+                            ))
+                for k, v in sorted(items):  # lexical order
+                    if isinstance(k, QName):
+                        k = k.text
+                    if isinstance(v, QName):
+                        v = qnames[v.text]
+                    else:
+                        v = _escape_attrib_html(v)
+                    # FIXME: handle boolean attributes
+                    write(" %s=\"%s\"" % (qnames[k], v))
+            write(">")
+            ltag = tag.lower()
+            if text:
+                if ltag == "script" or ltag == "style":
+                    write(text)
+                else:
+                    write(_escape_cdata(text))
+            for e in elem:
+                _serialize_html(write, e, qnames, None)
+            if ltag not in HTML_EMPTY:
+                write("</" + tag + ">")
+    if elem.tail:
+        write(_escape_cdata(elem.tail))
+
+def _serialize_text(write, elem):
+    for part in elem.itertext():
+        write(part)
+    if elem.tail:
+        write(elem.tail)
+
+_serialize = {
+    "xml": _serialize_xml,
+    "html": _serialize_html,
+    "text": _serialize_text,
+# this optional method is imported at the end of the module
+#   "c14n": _serialize_c14n,
+}
+
+
+def register_namespace(prefix, uri):
+    """Register a namespace prefix.
+
+    The registry is global, and any existing mapping for either the
+    given prefix or the namespace URI will be removed.
+
+    *prefix* is the namespace prefix, *uri* is a namespace uri. Tags and
+    attributes in this namespace will be serialized with prefix if possible.
+
+    ValueError is raised if prefix is reserved or is invalid.
+
+    """
+    if re.match(r"ns\d+$", prefix):
+        raise ValueError("Prefix format reserved for internal use")
+    for k, v in list(_namespace_map.items()):
+        if k == uri or v == prefix:
+            del _namespace_map[k]
+    _namespace_map[uri] = prefix
+
+_namespace_map = {
+    # "well-known" namespace prefixes
+    "http://www.w3.org/XML/1998/namespace": "xml",
+    "http://www.w3.org/1999/xhtml": "html",
+    "http://www.w3.org/1999/02/22-rdf-syntax-ns#": "rdf",
+    "http://schemas.xmlsoap.org/wsdl/": "wsdl",
+    # xml schema
+    "http://www.w3.org/2001/XMLSchema": "xs",
+    "http://www.w3.org/2001/XMLSchema-instance": "xsi",
+    # dublin core
+    "http://purl.org/dc/elements/1.1/": "dc",
+}
+# For tests and troubleshooting
+register_namespace._namespace_map = _namespace_map
+
+def _raise_serialization_error(text):
+    raise TypeError(
+        "cannot serialize %r (type %s)" % (text, type(text).__name__)
+        )
+
+def _escape_cdata(text):
+    # escape character data
+    try:
+        # it's worth avoiding do-nothing calls for strings that are
+        # shorter than 500 characters, or so.  assume that's, by far,
+        # the most common case in most applications.
+        if "&" in text:
+            text = text.replace("&", "&amp;")
+        if "<" in text:
+            text = text.replace("<", "&lt;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        return text
+    except (TypeError, AttributeError):
+        _raise_serialization_error(text)
+
+def _escape_attrib(text):
+    # escape attribute value
+    try:
+        if "&" in text:
+            text = text.replace("&", "&amp;")
+        if "<" in text:
+            text = text.replace("<", "&lt;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        if "\"" in text:
+            text = text.replace("\"", "&quot;")
+        # The following business with carriage returns is to satisfy
+        # Section 2.11 of the XML specification, stating that
+        # CR or CR LN should be replaced with just LN
+        # http://www.w3.org/TR/REC-xml/#sec-line-ends
+        if "\r\n" in text:
+            text = text.replace("\r\n", "\n")
+        if "\r" in text:
+            text = text.replace("\r", "\n")
+        #The following four lines are issue 17582
+        if "\n" in text:
+            text = text.replace("\n", "&#10;")
+        if "\t" in text:
+            text = text.replace("\t", "&#09;")
+        return text
+    except (TypeError, AttributeError):
+        _raise_serialization_error(text)
+
+def _escape_attrib_html(text):
+    # escape attribute value
+    try:
+        if "&" in text:
+            text = text.replace("&", "&amp;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        if "\"" in text:
+            text = text.replace("\"", "&quot;")
+        return text
+    except (TypeError, AttributeError):
+        _raise_serialization_error(text)
+
+# --------------------------------------------------------------------
+
+def tostring(element, encoding=None, method=None, *,
+             short_empty_elements=True):
+    """Generate string representation of XML element.
+
+    All subelements are included.  If encoding is "unicode", a string
+    is returned. Otherwise a bytestring is returned.
+
+    *element* is an Element instance, *encoding* is an optional output
+    encoding defaulting to US-ASCII, *method* is an optional output which can
+    be one of "xml" (default), "html", "text" or "c14n".
+
+    Returns an (optionally) encoded string containing the XML data.
+
+    """
+    stream = io.StringIO() if encoding == 'unicode' else io.BytesIO()
+    ElementTree(element).write(stream, encoding, method=method,
+                               short_empty_elements=short_empty_elements)
+    return stream.getvalue()
+
+class _ListDataStream(io.BufferedIOBase):
+    """An auxiliary stream accumulating into a list reference."""
+    def __init__(self, lst):
+        self.lst = lst
+
+    def writable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def write(self, b):
+        self.lst.append(b)
+
+    def tell(self):
+        return len(self.lst)
+
+def tostringlist(element, encoding=None, method=None, *,
+                 short_empty_elements=True):
+    lst = []
+    stream = _ListDataStream(lst)
+    ElementTree(element).write(stream, encoding, method=method,
+                               short_empty_elements=short_empty_elements)
+    return lst
+
+
+def dump(elem):
+    """Write element tree or element structure to sys.stdout.
+
+    This function should be used for debugging only.
+
+    *elem* is either an ElementTree, or a single Element.  The exact output
+    format is implementation dependent.  In this version, it's written as an
+    ordinary XML file.
+
+    """
+    # debugging
+    if not isinstance(elem, ElementTree):
+        elem = ElementTree(elem)
+    elem.write(sys.stdout, encoding="unicode")
+    tail = elem.getroot().tail
+    if not tail or tail[-1] != "\n":
+        sys.stdout.write("\n")
+
+# --------------------------------------------------------------------
+# parsing
+
+
+def parse(source, parser=None):
+    """Parse XML document into element tree.
+
+    *source* is a filename or file object containing XML data,
+    *parser* is an optional parser instance defaulting to XMLParser.
+
+    Return an ElementTree instance.
+
+    """
+    tree = ElementTree()
+    tree.parse(source, parser)
+    return tree
+
+
+def iterparse(source, events=None, parser=None):
+    """Incrementally parse XML document into ElementTree.
+
+    This class also reports what's going on to the user based on the
+    *events* it is initialized with.  The supported events are the strings
+    "start", "end", "start-ns" and "end-ns" (the "ns" events are used to get
+    detailed namespace information).  If *events* is omitted, only
+    "end" events are reported.
+
+    *source* is a filename or file object containing XML data, *events* is
+    a list of events to report back, *parser* is an optional parser instance.
+
+    Returns an iterator providing (event, elem) pairs.
+
+    """
+    # Use the internal, undocumented _parser argument for now; When the
+    # parser argument of iterparse is removed, this can be killed.
+    pullparser = XMLPullParser(events=events, _parser=parser)
+    def iterator():
+        try:
+            while True:
+                yield from pullparser.read_events()
+                # load event buffer
+                data = source.read(16 * 1024)
+                if not data:
+                    break
+                pullparser.feed(data)
+            root = pullparser._close_and_return_root()
+            yield from pullparser.read_events()
+            it.root = root
+        finally:
+            if close_source:
+                source.close()
+
+    class IterParseIterator(collections.Iterator):
+        __next__ = iterator().__next__
+    it = IterParseIterator()
+    it.root = None
+    del iterator, IterParseIterator
+
+    close_source = False
+    if not hasattr(source, "read"):
+        source = open(source, "rb")
+        close_source = True
+
+    return it
+
+
+class XMLPullParser:
+
+    def __init__(self, events=None, *, _parser=None):
+        # The _parser argument is for internal use only and must not be relied
+        # upon in user code. It will be removed in a future release.
+        # See http://bugs.python.org/issue17741 for more details.
+
+        self._events_queue = collections.deque()
+        self._parser = _parser or XMLParser(target=TreeBuilder())
+        # wire up the parser for event reporting
+        if events is None:
+            events = ("end",)
+        self._parser._setevents(self._events_queue, events)
+
+    def feed(self, data):
+        """Feed encoded data to parser."""
+        if self._parser is None:
+            raise ValueError("feed() called after end of stream")
+        if data:
+            try:
+                self._parser.feed(data)
+            except SyntaxError as exc:
+                self._events_queue.append(exc)
+
+    def _close_and_return_root(self):
+        # iterparse needs this to set its root attribute properly :(
+        root = self._parser.close()
+        self._parser = None
+        return root
+
+    def close(self):
+        """Finish feeding data to parser.
+
+        Unlike XMLParser, does not return the root element. Use
+        read_events() to consume elements from XMLPullParser.
+        """
+        self._close_and_return_root()
+
+    def read_events(self):
+        """Return an iterator over currently available (event, elem) pairs.
+
+        Events are consumed from the internal event queue as they are
+        retrieved from the iterator.
+        """
+        events = self._events_queue
+        while events:
+            event = events.popleft()
+            if isinstance(event, Exception):
+                raise event
+            else:
+                yield event
+
+
+def XML(text, parser=None):
+    """Parse XML document from string constant.
+
+    This function can be used to embed "XML Literals" in Python code.
+
+    *text* is a string containing XML data, *parser* is an
+    optional parser instance, defaulting to the standard XMLParser.
+
+    Returns an Element instance.
+
+    """
+    if not parser:
+        parser = XMLParser(target=TreeBuilder())
+    parser.feed(text)
+    return parser.close()
+
+
+def XMLID(text, parser=None):
+    """Parse XML document from string constant for its IDs.
+
+    *text* is a string containing XML data, *parser* is an
+    optional parser instance, defaulting to the standard XMLParser.
+
+    Returns an (Element, dict) tuple, in which the
+    dict maps element id:s to elements.
+
+    """
+    if not parser:
+        parser = XMLParser(target=TreeBuilder())
+    parser.feed(text)
+    tree = parser.close()
+    ids = {}
+    for elem in tree.iter():
+        id = elem.get("id")
+        if id:
+            ids[id] = elem
+    return tree, ids
+
+# Parse XML document from string constant.  Alias for XML().
+fromstring = XML
+
+def fromstringlist(sequence, parser=None):
+    """Parse XML document from sequence of string fragments.
+
+    *sequence* is a list of other sequence, *parser* is an optional parser
+    instance, defaulting to the standard XMLParser.
+
+    Returns an Element instance.
+
+    """
+    if not parser:
+        parser = XMLParser(target=TreeBuilder())
+    for text in sequence:
+        parser.feed(text)
+    return parser.close()
+
+# --------------------------------------------------------------------
+
+
+class TreeBuilder:
+    """Generic element structure builder.
+
+    This builder converts a sequence of start, data, and end method
+    calls to a well-formed element structure.
+
+    You can use this class to build an element structure using a custom XML
+    parser, or a parser for some other XML-like format.
+
+    *element_factory* is an optional element factory which is called
+    to create new Element instances, as necessary.
+
+    """
+    def __init__(self, element_factory=None):
+        self._data = [] # data collector
+        self._elem = [] # element stack
+        self._last = None # last element
+        self._tail = None # true if we're after an end tag
+        if element_factory is None:
+            element_factory = Element
+        self._factory = element_factory
+
+    def close(self):
+        """Flush builder buffers and return toplevel document Element."""
+        assert len(self._elem) == 0, "missing end tags"
+        assert self._last is not None, "missing toplevel element"
+        return self._last
+
+    def _flush(self):
+        if self._data:
+            if self._last is not None:
+                text = "".join(self._data)
+                if self._tail:
+                    assert self._last.tail is None, "internal error (tail)"
+                    self._last.tail = text
+                else:
+                    assert self._last.text is None, "internal error (text)"
+                    self._last.text = text
+            self._data = []
+
+    def data(self, data):
+        """Add text to current element."""
+        self._data.append(data)
+
+    def start(self, tag, attrs):
+        """Open new element and return it.
+
+        *tag* is the element name, *attrs* is a dict containing element
+        attributes.
+
+        """
+        self._flush()
+        self._last = elem = self._factory(tag, attrs)
+        if self._elem:
+            self._elem[-1].append(elem)
+        self._elem.append(elem)
+        self._tail = 0
+        return elem
+
+    def end(self, tag):
+        """Close and return current Element.
+
+        *tag* is the element name.
+
+        """
+        self._flush()
+        self._last = self._elem.pop()
+        assert self._last.tag == tag,\
+               "end tag mismatch (expected %s, got %s)" % (
+                   self._last.tag, tag)
+        self._tail = 1
+        return self._last
+
+
+# also see ElementTree and TreeBuilder
+class XMLParser:
+    """Element structure builder for XML source data based on the expat parser.
+
+    *html* are predefined HTML entities (deprecated and not supported),
+    *target* is an optional target object which defaults to an instance of the
+    standard TreeBuilder class, *encoding* is an optional encoding string
+    which if given, overrides the encoding specified in the XML file:
+    http://www.iana.org/assignments/character-sets
+
+    """
+
+    def __init__(self, html=0, target=None, encoding=None):
+        try:
+            from xml.parsers import expat
+        except ImportError:
+            try:
+                import pyexpat as expat
+            except ImportError:
+                raise ImportError(
+                    "No module named expat; use SimpleXMLTreeBuilder instead"
+                    )
+        parser = expat.ParserCreate(encoding, "}")
+        if target is None:
+            target = TreeBuilder()
+        # underscored names are provided for compatibility only
+        self.parser = self._parser = parser
+        self.target = self._target = target
+        self._error = expat.error
+        self._names = {} # name memo cache
+        # main callbacks
+        parser.DefaultHandlerExpand = self._default
+        if hasattr(target, 'start'):
+            parser.StartElementHandler = self._start
+        if hasattr(target, 'end'):
+            parser.EndElementHandler = self._end
+        if hasattr(target, 'data'):
+            parser.CharacterDataHandler = target.data
+        # miscellaneous callbacks
+        if hasattr(target, 'comment'):
+            parser.CommentHandler = target.comment
+        if hasattr(target, 'pi'):
+            parser.ProcessingInstructionHandler = target.pi
+        # Configure pyexpat: buffering, new-style attribute handling.
+        parser.buffer_text = 1
+        parser.ordered_attributes = 1
+        parser.specified_attributes = 1
+        self._doctype = None
+        self.entity = {}
+        try:
+            self.version = "Expat %d.%d.%d" % expat.version_info
+        except AttributeError:
+            pass # unknown
+
+    def _setevents(self, events_queue, events_to_report):
+        # Internal API for XMLPullParser
+        # events_to_report: a list of events to report during parsing (same as
+        # the *events* of XMLPullParser's constructor.
+        # events_queue: a list of actual parsing events that will be populated
+        # by the underlying parser.
+        #
+        parser = self._parser
+        append = events_queue.append
+        for event_name in events_to_report:
+            if event_name == "start":
+                parser.ordered_attributes = 1
+                parser.specified_attributes = 1
+                def handler(tag, attrib_in, event=event_name, append=append,
+                            start=self._start):
+                    append((event, start(tag, attrib_in)))
+                parser.StartElementHandler = handler
+            elif event_name == "end":
+                def handler(tag, event=event_name, append=append,
+                            end=self._end):
+                    append((event, end(tag)))
+                parser.EndElementHandler = handler
+            elif event_name == "start-ns":
+                def handler(prefix, uri, event=event_name, append=append):
+                    append((event, (prefix or "", uri or "")))
+                parser.StartNamespaceDeclHandler = handler
+            elif event_name == "end-ns":
+                def handler(prefix, event=event_name, append=append):
+                    append((event, None))
+                parser.EndNamespaceDeclHandler = handler
+            else:
+                raise ValueError("unknown event %r" % event_name)
+
+    def _raiseerror(self, value):
+        err = ParseError(value)
+        err.code = value.code
+        err.position = value.lineno, value.offset
+        raise err
+
+    def _fixname(self, key):
+        # expand qname, and convert name string to ascii, if possible
+        try:
+            name = self._names[key]
+        except KeyError:
+            name = key
+            if "}" in name:
+                name = "{" + name
+            self._names[key] = name
+        return name
+
+    def _start(self, tag, attr_list):
+        # Handler for expat's StartElementHandler. Since ordered_attributes
+        # is set, the attributes are reported as a list of alternating
+        # attribute name,value.
+        fixname = self._fixname
+        tag = fixname(tag)
+        attrib = {}
+        if attr_list:
+            for i in range(0, len(attr_list), 2):
+                attrib[fixname(attr_list[i])] = attr_list[i+1]
+        return self.target.start(tag, attrib)
+
+    def _end(self, tag):
+        return self.target.end(self._fixname(tag))
+
+    def _default(self, text):
+        prefix = text[:1]
+        if prefix == "&":
+            # deal with undefined entities
+            try:
+                data_handler = self.target.data
+            except AttributeError:
+                return
+            try:
+                data_handler(self.entity[text[1:-1]])
+            except KeyError:
+                from xml.parsers import expat
+                err = expat.error(
+                    "undefined entity %s: line %d, column %d" %
+                    (text, self.parser.ErrorLineNumber,
+                    self.parser.ErrorColumnNumber)
+                    )
+                err.code = 11 # XML_ERROR_UNDEFINED_ENTITY
+                err.lineno = self.parser.ErrorLineNumber
+                err.offset = self.parser.ErrorColumnNumber
+                raise err
+        elif prefix == "<" and text[:9] == "<!DOCTYPE":
+            self._doctype = [] # inside a doctype declaration
+        elif self._doctype is not None:
+            # parse doctype contents
+            if prefix == ">":
+                self._doctype = None
+                return
+            text = text.strip()
+            if not text:
+                return
+            self._doctype.append(text)
+            n = len(self._doctype)
+            if n > 2:
+                type = self._doctype[1]
+                if type == "PUBLIC" and n == 4:
+                    name, type, pubid, system = self._doctype
+                    if pubid:
+                        pubid = pubid[1:-1]
+                elif type == "SYSTEM" and n == 3:
+                    name, type, system = self._doctype
+                    pubid = None
+                else:
+                    return
+                if hasattr(self.target, "doctype"):
+                    self.target.doctype(name, pubid, system[1:-1])
+                elif self.doctype != self._XMLParser__doctype:
+                    # warn about deprecated call
+                    self._XMLParser__doctype(name, pubid, system[1:-1])
+                    self.doctype(name, pubid, system[1:-1])
+                self._doctype = None
+
+    def doctype(self, name, pubid, system):
+        """(Deprecated)  Handle doctype declaration
+
+        *name* is the Doctype name, *pubid* is the public identifier,
+        and *system* is the system identifier.
+
+        """
+        warnings.warn(
+            "This method of XMLParser is deprecated.  Define doctype() "
+            "method on the TreeBuilder target.",
+            DeprecationWarning,
+            )
+
+    # sentinel, if doctype is redefined in a subclass
+    __doctype = doctype
+
+    def feed(self, data):
+        """Feed encoded data to parser."""
+        try:
+            self.parser.Parse(data, 0)
+        except self._error as v:
+            self._raiseerror(v)
+
+    def close(self):
+        """Finish feeding data to parser and return element structure."""
+        try:
+            self.parser.Parse("", 1) # end of data
+        except self._error as v:
+            self._raiseerror(v)
+        try:
+            close_handler = self.target.close
+        except AttributeError:
+            pass
+        else:
+            return close_handler()
+        finally:
+            # get rid of circular references
+            del self.parser, self._parser
+            del self.target, self._target
+
+
+# Import the C accelerators
+try:
+    # Element is going to be shadowed by the C implementation. We need to keep
+    # the Python version of it accessible for some "creative" by external code
+    # (see tests)
+    _Element_Py = Element
+
+    # Element, SubElement, ParseError, TreeBuilder, XMLParser
+    from _elementtree import *
+except ImportError:
+    pass
diff --git a/Lib/xml/etree/__init__.py b/Lib/xml/etree/__init__.py
new file mode 100644
index 000000000..27fd8f6d4
--- /dev/null
+++ b/Lib/xml/etree/__init__.py
@@ -0,0 +1,33 @@
+# $Id: __init__.py 3375 2008-02-13 08:05:08Z fredrik $
+# elementtree package
+
+# --------------------------------------------------------------------
+# The ElementTree toolkit is
+#
+# Copyright (c) 1999-2008 by Fredrik Lundh
+#
+# By obtaining, using, and/or copying this software and/or its
+# associated documentation, you agree that you have read, understood,
+# and will comply with the following terms and conditions:
+#
+# Permission to use, copy, modify, and distribute this software and
+# its associated documentation for any purpose and without fee is
+# hereby granted, provided that the above copyright notice appears in
+# all copies, and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of
+# Secret Labs AB or the author not be used in advertising or publicity
+# pertaining to distribution of the software without specific, written
+# prior permission.
+#
+# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
+# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
+# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+# --------------------------------------------------------------------
+
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/psf/license for licensing details.
diff --git a/Lib/xml/etree/cElementTree.py b/Lib/xml/etree/cElementTree.py
new file mode 100644
index 000000000..368e67918
--- /dev/null
+++ b/Lib/xml/etree/cElementTree.py
@@ -0,0 +1,3 @@
+# Deprecated alias for xml.etree.ElementTree
+
+from xml.etree.ElementTree import *
diff --git a/Lib/xml/parsers/__init__.py b/Lib/xml/parsers/__init__.py
new file mode 100644
index 000000000..eb314a3b4
--- /dev/null
+++ b/Lib/xml/parsers/__init__.py
@@ -0,0 +1,8 @@
+"""Python interfaces to XML parsers.
+
+This package contains one module:
+
+expat -- Python wrapper for James Clark's Expat parser, with namespace
+         support.
+
+"""
diff --git a/Lib/xml/parsers/expat.py b/Lib/xml/parsers/expat.py
new file mode 100644
index 000000000..bcbe9fb1f
--- /dev/null
+++ b/Lib/xml/parsers/expat.py
@@ -0,0 +1,8 @@
+"""Interface to the Expat non-validating XML parser."""
+import sys
+
+from pyexpat import *
+
+# provide pyexpat submodules as xml.parsers.expat submodules
+sys.modules['xml.parsers.expat.model'] = model
+sys.modules['xml.parsers.expat.errors'] = errors
diff --git a/Lib/xml/sax/__init__.py b/Lib/xml/sax/__init__.py
new file mode 100644
index 000000000..13f6cf58d
--- /dev/null
+++ b/Lib/xml/sax/__init__.py
@@ -0,0 +1,107 @@
+"""Simple API for XML (SAX) implementation for Python.
+
+This module provides an implementation of the SAX 2 interface;
+information about the Java version of the interface can be found at
+http://www.megginson.com/SAX/.  The Python version of the interface is
+documented at <...>.
+
+This package contains the following modules:
+
+handler -- Base classes and constants which define the SAX 2 API for
+           the 'client-side' of SAX for Python.
+
+saxutils -- Implementation of the convenience classes commonly used to
+            work with SAX.
+
+xmlreader -- Base classes and constants which define the SAX 2 API for
+             the parsers used with SAX for Python.
+
+expatreader -- Driver that allows use of the Expat parser with SAX.
+"""
+
+from .xmlreader import InputSource
+from .handler import ContentHandler, ErrorHandler
+from ._exceptions import SAXException, SAXNotRecognizedException, \
+                        SAXParseException, SAXNotSupportedException, \
+                        SAXReaderNotAvailable
+
+
+def parse(source, handler, errorHandler=ErrorHandler()):
+    parser = make_parser()
+    parser.setContentHandler(handler)
+    parser.setErrorHandler(errorHandler)
+    parser.parse(source)
+
+def parseString(string, handler, errorHandler=ErrorHandler()):
+    import io
+    if errorHandler is None:
+        errorHandler = ErrorHandler()
+    parser = make_parser()
+    parser.setContentHandler(handler)
+    parser.setErrorHandler(errorHandler)
+
+    inpsrc = InputSource()
+    if isinstance(string, str):
+        inpsrc.setCharacterStream(io.StringIO(string))
+    else:
+        inpsrc.setByteStream(io.BytesIO(string))
+    parser.parse(inpsrc)
+
+# this is the parser list used by the make_parser function if no
+# alternatives are given as parameters to the function
+
+default_parser_list = ["xml.sax.expatreader"]
+
+# tell modulefinder that importing sax potentially imports expatreader
+_false = 0
+if _false:
+    import xml.sax.expatreader
+
+import os, sys
+if not sys.flags.ignore_environment and "PY_SAX_PARSER" in os.environ:
+    default_parser_list = os.environ["PY_SAX_PARSER"].split(",")
+del os
+
+_key = "python.xml.sax.parser"
+if sys.platform[:4] == "java" and sys.registry.containsKey(_key):
+    default_parser_list = sys.registry.getProperty(_key).split(",")
+
+
+def make_parser(parser_list = []):
+    """Creates and returns a SAX parser.
+
+    Creates the first parser it is able to instantiate of the ones
+    given in the list created by doing parser_list +
+    default_parser_list.  The lists must contain the names of Python
+    modules containing both a SAX parser and a create_parser function."""
+
+    for parser_name in parser_list + default_parser_list:
+        try:
+            return _create_parser(parser_name)
+        except ImportError as e:
+            import sys
+            if parser_name in sys.modules:
+                # The parser module was found, but importing it
+                # failed unexpectedly, pass this exception through
+                raise
+        except SAXReaderNotAvailable:
+            # The parser module detected that it won't work properly,
+            # so try the next one
+            pass
+
+    raise SAXReaderNotAvailable("No parsers found", None)
+
+# --- Internal utility methods used by make_parser
+
+if sys.platform[ : 4] == "java":
+    def _create_parser(parser_name):
+        from org.python.core import imp
+        drv_module = imp.importName(parser_name, 0, globals())
+        return drv_module.create_parser()
+
+else:
+    def _create_parser(parser_name):
+        drv_module = __import__(parser_name,{},{},['create_parser'])
+        return drv_module.create_parser()
+
+del sys
diff --git a/Lib/xml/sax/_exceptions.py b/Lib/xml/sax/_exceptions.py
new file mode 100644
index 000000000..a9b2ba35c
--- /dev/null
+++ b/Lib/xml/sax/_exceptions.py
@@ -0,0 +1,131 @@
+"""Different kinds of SAX Exceptions"""
+import sys
+if sys.platform[:4] == "java":
+    from java.lang import Exception
+del sys
+
+# ===== SAXEXCEPTION =====
+
+class SAXException(Exception):
+    """Encapsulate an XML error or warning. This class can contain
+    basic error or warning information from either the XML parser or
+    the application: you can subclass it to provide additional
+    functionality, or to add localization. Note that although you will
+    receive a SAXException as the argument to the handlers in the
+    ErrorHandler interface, you are not actually required to raise
+    the exception; instead, you can simply read the information in
+    it."""
+
+    def __init__(self, msg, exception=None):
+        """Creates an exception. The message is required, but the exception
+        is optional."""
+        self._msg = msg
+        self._exception = exception
+        Exception.__init__(self, msg)
+
+    def getMessage(self):
+        "Return a message for this exception."
+        return self._msg
+
+    def getException(self):
+        "Return the embedded exception, or None if there was none."
+        return self._exception
+
+    def __str__(self):
+        "Create a string representation of the exception."
+        return self._msg
+
+    def __getitem__(self, ix):
+        """Avoids weird error messages if someone does exception[ix] by
+        mistake, since Exception has __getitem__ defined."""
+        raise AttributeError("__getitem__")
+
+
+# ===== SAXPARSEEXCEPTION =====
+
+class SAXParseException(SAXException):
+    """Encapsulate an XML parse error or warning.
+
+    This exception will include information for locating the error in
+    the original XML document. Note that although the application will
+    receive a SAXParseException as the argument to the handlers in the
+    ErrorHandler interface, the application is not actually required
+    to raise the exception; instead, it can simply read the
+    information in it and take a different action.
+
+    Since this exception is a subclass of SAXException, it inherits
+    the ability to wrap another exception."""
+
+    def __init__(self, msg, exception, locator):
+        "Creates the exception. The exception parameter is allowed to be None."
+        SAXException.__init__(self, msg, exception)
+        self._locator = locator
+
+        # We need to cache this stuff at construction time.
+        # If this exception is raised, the objects through which we must
+        # traverse to get this information may be deleted by the time
+        # it gets caught.
+        self._systemId = self._locator.getSystemId()
+        self._colnum = self._locator.getColumnNumber()
+        self._linenum = self._locator.getLineNumber()
+
+    def getColumnNumber(self):
+        """The column number of the end of the text where the exception
+        occurred."""
+        return self._colnum
+
+    def getLineNumber(self):
+        "The line number of the end of the text where the exception occurred."
+        return self._linenum
+
+    def getPublicId(self):
+        "Get the public identifier of the entity where the exception occurred."
+        return self._locator.getPublicId()
+
+    def getSystemId(self):
+        "Get the system identifier of the entity where the exception occurred."
+        return self._systemId
+
+    def __str__(self):
+        "Create a string representation of the exception."
+        sysid = self.getSystemId()
+        if sysid is None:
+            sysid = "<unknown>"
+        linenum = self.getLineNumber()
+        if linenum is None:
+            linenum = "?"
+        colnum = self.getColumnNumber()
+        if colnum is None:
+            colnum = "?"
+        return "%s:%s:%s: %s" % (sysid, linenum, colnum, self._msg)
+
+
+# ===== SAXNOTRECOGNIZEDEXCEPTION =====
+
+class SAXNotRecognizedException(SAXException):
+    """Exception class for an unrecognized identifier.
+
+    An XMLReader will raise this exception when it is confronted with an
+    unrecognized feature or property. SAX applications and extensions may
+    use this class for similar purposes."""
+
+
+# ===== SAXNOTSUPPORTEDEXCEPTION =====
+
+class SAXNotSupportedException(SAXException):
+    """Exception class for an unsupported operation.
+
+    An XMLReader will raise this exception when a service it cannot
+    perform is requested (specifically setting a state or value). SAX
+    applications and extensions may use this class for similar
+    purposes."""
+
+# ===== SAXNOTSUPPORTEDEXCEPTION =====
+
+class SAXReaderNotAvailable(SAXNotSupportedException):
+    """Exception class for a missing driver.
+
+    An XMLReader module (driver) should raise this exception when it
+    is first imported, e.g. when a support module cannot be imported.
+    It also may be raised during parsing, e.g. if executing an external
+    program is not permitted."""
diff --git a/Lib/xml/sax/expatreader.py b/Lib/xml/sax/expatreader.py
new file mode 100644
index 000000000..5066ffc2f
--- /dev/null
+++ b/Lib/xml/sax/expatreader.py
@@ -0,0 +1,446 @@
+"""
+SAX driver for the pyexpat C module.  This driver works with
+pyexpat.__version__ == '2.22'.
+"""
+
+version = "0.20"
+
+from xml.sax._exceptions import *
+from xml.sax.handler import feature_validation, feature_namespaces
+from xml.sax.handler import feature_namespace_prefixes
+from xml.sax.handler import feature_external_ges, feature_external_pes
+from xml.sax.handler import feature_string_interning
+from xml.sax.handler import property_xml_string, property_interning_dict
+
+# xml.parsers.expat does not raise ImportError in Jython
+import sys
+if sys.platform[:4] == "java":
+    raise SAXReaderNotAvailable("expat not available in Java", None)
+del sys
+
+try:
+    from xml.parsers import expat
+except ImportError:
+    raise SAXReaderNotAvailable("expat not supported", None)
+else:
+    if not hasattr(expat, "ParserCreate"):
+        raise SAXReaderNotAvailable("expat not supported", None)
+from xml.sax import xmlreader, saxutils, handler
+
+AttributesImpl = xmlreader.AttributesImpl
+AttributesNSImpl = xmlreader.AttributesNSImpl
+
+# If we're using a sufficiently recent version of Python, we can use
+# weak references to avoid cycles between the parser and content
+# handler, otherwise we'll just have to pretend.
+try:
+    import _weakref
+except ImportError:
+    def _mkproxy(o):
+        return o
+else:
+    import weakref
+    _mkproxy = weakref.proxy
+    del weakref, _weakref
+
+class _ClosedParser:
+    pass
+
+# --- ExpatLocator
+
+class ExpatLocator(xmlreader.Locator):
+    """Locator for use with the ExpatParser class.
+
+    This uses a weak reference to the parser object to avoid creating
+    a circular reference between the parser and the content handler.
+    """
+    def __init__(self, parser):
+        self._ref = _mkproxy(parser)
+
+    def getColumnNumber(self):
+        parser = self._ref
+        if parser._parser is None:
+            return None
+        return parser._parser.ErrorColumnNumber
+
+    def getLineNumber(self):
+        parser = self._ref
+        if parser._parser is None:
+            return 1
+        return parser._parser.ErrorLineNumber
+
+    def getPublicId(self):
+        parser = self._ref
+        if parser is None:
+            return None
+        return parser._source.getPublicId()
+
+    def getSystemId(self):
+        parser = self._ref
+        if parser is None:
+            return None
+        return parser._source.getSystemId()
+
+
+# --- ExpatParser
+
+class ExpatParser(xmlreader.IncrementalParser, xmlreader.Locator):
+    """SAX driver for the pyexpat C module."""
+
+    def __init__(self, namespaceHandling=0, bufsize=2**16-20):
+        xmlreader.IncrementalParser.__init__(self, bufsize)
+        self._source = xmlreader.InputSource()
+        self._parser = None
+        self._namespaces = namespaceHandling
+        self._lex_handler_prop = None
+        self._parsing = 0
+        self._entity_stack = []
+        self._external_ges = 0
+        self._interning = None
+
+    # XMLReader methods
+
+    def parse(self, source):
+        "Parse an XML document from a URL or an InputSource."
+        source = saxutils.prepare_input_source(source)
+
+        self._source = source
+        try:
+            self.reset()
+            self._cont_handler.setDocumentLocator(ExpatLocator(self))
+            xmlreader.IncrementalParser.parse(self, source)
+        except:
+            # bpo-30264: Close the source on error to not leak resources:
+            # xml.sax.parse() doesn't give access to the underlying parser
+            # to the caller
+            self._close_source()
+            raise
+
+    def prepareParser(self, source):
+        if source.getSystemId() is not None:
+            self._parser.SetBase(source.getSystemId())
+
+    # Redefined setContentHandler to allow changing handlers during parsing
+
+    def setContentHandler(self, handler):
+        xmlreader.IncrementalParser.setContentHandler(self, handler)
+        if self._parsing:
+            self._reset_cont_handler()
+
+    def getFeature(self, name):
+        if name == feature_namespaces:
+            return self._namespaces
+        elif name == feature_string_interning:
+            return self._interning is not None
+        elif name in (feature_validation, feature_external_pes,
+                      feature_namespace_prefixes):
+            return 0
+        elif name == feature_external_ges:
+            return self._external_ges
+        raise SAXNotRecognizedException("Feature '%s' not recognized" % name)
+
+    def setFeature(self, name, state):
+        if self._parsing:
+            raise SAXNotSupportedException("Cannot set features while parsing")
+
+        if name == feature_namespaces:
+            self._namespaces = state
+        elif name == feature_external_ges:
+            self._external_ges = state
+        elif name == feature_string_interning:
+            if state:
+                if self._interning is None:
+                    self._interning = {}
+            else:
+                self._interning = None
+        elif name == feature_validation:
+            if state:
+                raise SAXNotSupportedException(
+                    "expat does not support validation")
+        elif name == feature_external_pes:
+            if state:
+                raise SAXNotSupportedException(
+                    "expat does not read external parameter entities")
+        elif name == feature_namespace_prefixes:
+            if state:
+                raise SAXNotSupportedException(
+                    "expat does not report namespace prefixes")
+        else:
+            raise SAXNotRecognizedException(
+                "Feature '%s' not recognized" % name)
+
+    def getProperty(self, name):
+        if name == handler.property_lexical_handler:
+            return self._lex_handler_prop
+        elif name == property_interning_dict:
+            return self._interning
+        elif name == property_xml_string:
+            if self._parser:
+                if hasattr(self._parser, "GetInputContext"):
+                    return self._parser.GetInputContext()
+                else:
+                    raise SAXNotRecognizedException(
+                        "This version of expat does not support getting"
+                        " the XML string")
+            else:
+                raise SAXNotSupportedException(
+                    "XML string cannot be returned when not parsing")
+        raise SAXNotRecognizedException("Property '%s' not recognized" % name)
+
+    def setProperty(self, name, value):
+        if name == handler.property_lexical_handler:
+            self._lex_handler_prop = value
+            if self._parsing:
+                self._reset_lex_handler_prop()
+        elif name == property_interning_dict:
+            self._interning = value
+        elif name == property_xml_string:
+            raise SAXNotSupportedException("Property '%s' cannot be set" %
+                                           name)
+        else:
+            raise SAXNotRecognizedException("Property '%s' not recognized" %
+                                            name)
+
+    # IncrementalParser methods
+
+    def feed(self, data, isFinal = 0):
+        if not self._parsing:
+            self.reset()
+            self._parsing = 1
+            self._cont_handler.startDocument()
+
+        try:
+            # The isFinal parameter is internal to the expat reader.
+            # If it is set to true, expat will check validity of the entire
+            # document. When feeding chunks, they are not normally final -
+            # except when invoked from close.
+            self._parser.Parse(data, isFinal)
+        except expat.error as e:
+            exc = SAXParseException(expat.ErrorString(e.code), e, self)
+            # FIXME: when to invoke error()?
+            self._err_handler.fatalError(exc)
+
+    def _close_source(self):
+        source = self._source
+        try:
+            file = source.getCharacterStream()
+            if file is not None:
+                file.close()
+        finally:
+            file = source.getByteStream()
+            if file is not None:
+                file.close()
+
+    def close(self):
+        if (self._entity_stack or self._parser is None or
+            isinstance(self._parser, _ClosedParser)):
+            # If we are completing an external entity, do nothing here
+            return
+        try:
+            self.feed("", isFinal = 1)
+            self._cont_handler.endDocument()
+            self._parsing = 0
+            # break cycle created by expat handlers pointing to our methods
+            self._parser = None
+        finally:
+            self._parsing = 0
+            if self._parser is not None:
+                # Keep ErrorColumnNumber and ErrorLineNumber after closing.
+                parser = _ClosedParser()
+                parser.ErrorColumnNumber = self._parser.ErrorColumnNumber
+                parser.ErrorLineNumber = self._parser.ErrorLineNumber
+                self._parser = parser
+            self._close_source()
+
+    def _reset_cont_handler(self):
+        self._parser.ProcessingInstructionHandler = \
+                                    self._cont_handler.processingInstruction
+        self._parser.CharacterDataHandler = self._cont_handler.characters
+
+    def _reset_lex_handler_prop(self):
+        lex = self._lex_handler_prop
+        parser = self._parser
+        if lex is None:
+            parser.CommentHandler = None
+            parser.StartCdataSectionHandler = None
+            parser.EndCdataSectionHandler = None
+            parser.StartDoctypeDeclHandler = None
+            parser.EndDoctypeDeclHandler = None
+        else:
+            parser.CommentHandler = lex.comment
+            parser.StartCdataSectionHandler = lex.startCDATA
+            parser.EndCdataSectionHandler = lex.endCDATA
+            parser.StartDoctypeDeclHandler = self.start_doctype_decl
+            parser.EndDoctypeDeclHandler = lex.endDTD
+
+    def reset(self):
+        if self._namespaces:
+            self._parser = expat.ParserCreate(self._source.getEncoding(), " ",
+                                              intern=self._interning)
+            self._parser.namespace_prefixes = 1
+            self._parser.StartElementHandler = self.start_element_ns
+            self._parser.EndElementHandler = self.end_element_ns
+        else:
+            self._parser = expat.ParserCreate(self._source.getEncoding(),
+                                              intern = self._interning)
+            self._parser.StartElementHandler = self.start_element
+            self._parser.EndElementHandler = self.end_element
+
+        self._reset_cont_handler()
+        self._parser.UnparsedEntityDeclHandler = self.unparsed_entity_decl
+        self._parser.NotationDeclHandler = self.notation_decl
+        self._parser.StartNamespaceDeclHandler = self.start_namespace_decl
+        self._parser.EndNamespaceDeclHandler = self.end_namespace_decl
+
+        self._decl_handler_prop = None
+        if self._lex_handler_prop:
+            self._reset_lex_handler_prop()
+#         self._parser.DefaultHandler =
+#         self._parser.DefaultHandlerExpand =
+#         self._parser.NotStandaloneHandler =
+        self._parser.ExternalEntityRefHandler = self.external_entity_ref
+        try:
+            self._parser.SkippedEntityHandler = self.skipped_entity_handler
+        except AttributeError:
+            # This pyexpat does not support SkippedEntity
+            pass
+        self._parser.SetParamEntityParsing(
+            expat.XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE)
+
+        self._parsing = 0
+        self._entity_stack = []
+
+    # Locator methods
+
+    def getColumnNumber(self):
+        if self._parser is None:
+            return None
+        return self._parser.ErrorColumnNumber
+
+    def getLineNumber(self):
+        if self._parser is None:
+            return 1
+        return self._parser.ErrorLineNumber
+
+    def getPublicId(self):
+        return self._source.getPublicId()
+
+    def getSystemId(self):
+        return self._source.getSystemId()
+
+    # event handlers
+    def start_element(self, name, attrs):
+        self._cont_handler.startElement(name, AttributesImpl(attrs))
+
+    def end_element(self, name):
+        self._cont_handler.endElement(name)
+
+    def start_element_ns(self, name, attrs):
+        pair = name.split()
+        if len(pair) == 1:
+            # no namespace
+            pair = (None, name)
+        elif len(pair) == 3:
+            pair = pair[0], pair[1]
+        else:
+            # default namespace
+            pair = tuple(pair)
+
+        newattrs = {}
+        qnames = {}
+        for (aname, value) in attrs.items():
+            parts = aname.split()
+            length = len(parts)
+            if length == 1:
+                # no namespace
+                qname = aname
+                apair = (None, aname)
+            elif length == 3:
+                qname = "%s:%s" % (parts[2], parts[1])
+                apair = parts[0], parts[1]
+            else:
+                # default namespace
+                qname = parts[1]
+                apair = tuple(parts)
+
+            newattrs[apair] = value
+            qnames[apair] = qname
+
+        self._cont_handler.startElementNS(pair, None,
+                                          AttributesNSImpl(newattrs, qnames))
+
+    def end_element_ns(self, name):
+        pair = name.split()
+        if len(pair) == 1:
+            pair = (None, name)
+        elif len(pair) == 3:
+            pair = pair[0], pair[1]
+        else:
+            pair = tuple(pair)
+
+        self._cont_handler.endElementNS(pair, None)
+
+    # this is not used (call directly to ContentHandler)
+    def processing_instruction(self, target, data):
+        self._cont_handler.processingInstruction(target, data)
+
+    # this is not used (call directly to ContentHandler)
+    def character_data(self, data):
+        self._cont_handler.characters(data)
+
+    def start_namespace_decl(self, prefix, uri):
+        self._cont_handler.startPrefixMapping(prefix, uri)
+
+    def end_namespace_decl(self, prefix):
+        self._cont_handler.endPrefixMapping(prefix)
+
+    def start_doctype_decl(self, name, sysid, pubid, has_internal_subset):
+        self._lex_handler_prop.startDTD(name, pubid, sysid)
+
+    def unparsed_entity_decl(self, name, base, sysid, pubid, notation_name):
+        self._dtd_handler.unparsedEntityDecl(name, pubid, sysid, notation_name)
+
+    def notation_decl(self, name, base, sysid, pubid):
+        self._dtd_handler.notationDecl(name, pubid, sysid)
+
+    def external_entity_ref(self, context, base, sysid, pubid):
+        if not self._external_ges:
+            return 1
+
+        source = self._ent_handler.resolveEntity(pubid, sysid)
+        source = saxutils.prepare_input_source(source,
+                                               self._source.getSystemId() or
+                                               "")
+
+        self._entity_stack.append((self._parser, self._source))
+        self._parser = self._parser.ExternalEntityParserCreate(context)
+        self._source = source
+
+        try:
+            xmlreader.IncrementalParser.parse(self, source)
+        except:
+            return 0  # FIXME: save error info here?
+
+        (self._parser, self._source) = self._entity_stack[-1]
+        del self._entity_stack[-1]
+        return 1
+
+    def skipped_entity_handler(self, name, is_pe):
+        if is_pe:
+            # The SAX spec requires to report skipped PEs with a '%'
+            name = '%'+name
+        self._cont_handler.skippedEntity(name)
+
+# ---
+
+def create_parser(*args, **kwargs):
+    return ExpatParser(*args, **kwargs)
+
+# ---
+
+if __name__ == "__main__":
+    import xml.sax.saxutils
+    p = create_parser()
+    p.setContentHandler(xml.sax.saxutils.XMLGenerator())
+    p.setErrorHandler(xml.sax.ErrorHandler())
+    p.parse("http://www.ibiblio.org/xml/examples/shakespeare/hamlet.xml")
diff --git a/Lib/xml/sax/handler.py b/Lib/xml/sax/handler.py
new file mode 100644
index 000000000..481733d2c
--- /dev/null
+++ b/Lib/xml/sax/handler.py
@@ -0,0 +1,342 @@
+"""
+This module contains the core classes of version 2.0 of SAX for Python.
+This file provides only default classes with absolutely minimum
+functionality, from which drivers and applications can be subclassed.
+
+Many of these classes are empty and are included only as documentation
+of the interfaces.
+
+$Id$
+"""
+
+version = '2.0beta'
+
+#============================================================================
+#
+# HANDLER INTERFACES
+#
+#============================================================================
+
+# ===== ERRORHANDLER =====
+
+class ErrorHandler:
+    """Basic interface for SAX error handlers.
+
+    If you create an object that implements this interface, then
+    register the object with your XMLReader, the parser will call the
+    methods in your object to report all warnings and errors. There
+    are three levels of errors available: warnings, (possibly)
+    recoverable errors, and unrecoverable errors. All methods take a
+    SAXParseException as the only parameter."""
+
+    def error(self, exception):
+        "Handle a recoverable error."
+        raise exception
+
+    def fatalError(self, exception):
+        "Handle a non-recoverable error."
+        raise exception
+
+    def warning(self, exception):
+        "Handle a warning."
+        print(exception)
+
+
+# ===== CONTENTHANDLER =====
+
+class ContentHandler:
+    """Interface for receiving logical document content events.
+
+    This is the main callback interface in SAX, and the one most
+    important to applications. The order of events in this interface
+    mirrors the order of the information in the document."""
+
+    def __init__(self):
+        self._locator = None
+
+    def setDocumentLocator(self, locator):
+        """Called by the parser to give the application a locator for
+        locating the origin of document events.
+
+        SAX parsers are strongly encouraged (though not absolutely
+        required) to supply a locator: if it does so, it must supply
+        the locator to the application by invoking this method before
+        invoking any of the other methods in the DocumentHandler
+        interface.
+
+        The locator allows the application to determine the end
+        position of any document-related event, even if the parser is
+        not reporting an error. Typically, the application will use
+        this information for reporting its own errors (such as
+        character content that does not match an application's
+        business rules). The information returned by the locator is
+        probably not sufficient for use with a search engine.
+
+        Note that the locator will return correct information only
+        during the invocation of the events in this interface. The
+        application should not attempt to use it at any other time."""
+        self._locator = locator
+
+    def startDocument(self):
+        """Receive notification of the beginning of a document.
+
+        The SAX parser will invoke this method only once, before any
+        other methods in this interface or in DTDHandler (except for
+        setDocumentLocator)."""
+
+    def endDocument(self):
+        """Receive notification of the end of a document.
+
+        The SAX parser will invoke this method only once, and it will
+        be the last method invoked during the parse. The parser shall
+        not invoke this method until it has either abandoned parsing
+        (because of an unrecoverable error) or reached the end of
+        input."""
+
+    def startPrefixMapping(self, prefix, uri):
+        """Begin the scope of a prefix-URI Namespace mapping.
+
+        The information from this event is not necessary for normal
+        Namespace processing: the SAX XML reader will automatically
+        replace prefixes for element and attribute names when the
+        http://xml.org/sax/features/namespaces feature is true (the
+        default).
+
+        There are cases, however, when applications need to use
+        prefixes in character data or in attribute values, where they
+        cannot safely be expanded automatically; the
+        start/endPrefixMapping event supplies the information to the
+        application to expand prefixes in those contexts itself, if
+        necessary.
+
+        Note that start/endPrefixMapping events are not guaranteed to
+        be properly nested relative to each-other: all
+        startPrefixMapping events will occur before the corresponding
+        startElement event, and all endPrefixMapping events will occur
+        after the corresponding endElement event, but their order is
+        not guaranteed."""
+
+    def endPrefixMapping(self, prefix):
+        """End the scope of a prefix-URI mapping.
+
+        See startPrefixMapping for details. This event will always
+        occur after the corresponding endElement event, but the order
+        of endPrefixMapping events is not otherwise guaranteed."""
+
+    def startElement(self, name, attrs):
+        """Signals the start of an element in non-namespace mode.
+
+        The name parameter contains the raw XML 1.0 name of the
+        element type as a string and the attrs parameter holds an
+        instance of the Attributes class containing the attributes of
+        the element."""
+
+    def endElement(self, name):
+        """Signals the end of an element in non-namespace mode.
+
+        The name parameter contains the name of the element type, just
+        as with the startElement event."""
+
+    def startElementNS(self, name, qname, attrs):
+        """Signals the start of an element in namespace mode.
+
+        The name parameter contains the name of the element type as a
+        (uri, localname) tuple, the qname parameter the raw XML 1.0
+        name used in the source document, and the attrs parameter
+        holds an instance of the Attributes class containing the
+        attributes of the element.
+
+        The uri part of the name tuple is None for elements which have
+        no namespace."""
+
+    def endElementNS(self, name, qname):
+        """Signals the end of an element in namespace mode.
+
+        The name parameter contains the name of the element type, just
+        as with the startElementNS event."""
+
+    def characters(self, content):
+        """Receive notification of character data.
+
+        The Parser will call this method to report each chunk of
+        character data. SAX parsers may return all contiguous
+        character data in a single chunk, or they may split it into
+        several chunks; however, all of the characters in any single
+        event must come from the same external entity so that the
+        Locator provides useful information."""
+
+    def ignorableWhitespace(self, whitespace):
+        """Receive notification of ignorable whitespace in element content.
+
+        Validating Parsers must use this method to report each chunk
+        of ignorable whitespace (see the W3C XML 1.0 recommendation,
+        section 2.10): non-validating parsers may also use this method
+        if they are capable of parsing and using content models.
+
+        SAX parsers may return all contiguous whitespace in a single
+        chunk, or they may split it into several chunks; however, all
+        of the characters in any single event must come from the same
+        external entity, so that the Locator provides useful
+        information."""
+
+    def processingInstruction(self, target, data):
+        """Receive notification of a processing instruction.
+
+        The Parser will invoke this method once for each processing
+        instruction found: note that processing instructions may occur
+        before or after the main document element.
+
+        A SAX parser should never report an XML declaration (XML 1.0,
+        section 2.8) or a text declaration (XML 1.0, section 4.3.1)
+        using this method."""
+
+    def skippedEntity(self, name):
+        """Receive notification of a skipped entity.
+
+        The Parser will invoke this method once for each entity
+        skipped. Non-validating processors may skip entities if they
+        have not seen the declarations (because, for example, the
+        entity was declared in an external DTD subset). All processors
+        may skip external entities, depending on the values of the
+        http://xml.org/sax/features/external-general-entities and the
+        http://xml.org/sax/features/external-parameter-entities
+        properties."""
+
+
+# ===== DTDHandler =====
+
+class DTDHandler:
+    """Handle DTD events.
+
+    This interface specifies only those DTD events required for basic
+    parsing (unparsed entities and attributes)."""
+
+    def notationDecl(self, name, publicId, systemId):
+        "Handle a notation declaration event."
+
+    def unparsedEntityDecl(self, name, publicId, systemId, ndata):
+        "Handle an unparsed entity declaration event."
+
+
+# ===== ENTITYRESOLVER =====
+
+class EntityResolver:
+    """Basic interface for resolving entities. If you create an object
+    implementing this interface, then register the object with your
+    Parser, the parser will call the method in your object to
+    resolve all external entities. Note that DefaultHandler implements
+    this interface with the default behaviour."""
+
+    def resolveEntity(self, publicId, systemId):
+        """Resolve the system identifier of an entity and return either
+        the system identifier to read from as a string, or an InputSource
+        to read from."""
+        return systemId
+
+
+#============================================================================
+#
+# CORE FEATURES
+#
+#============================================================================
+
+feature_namespaces = "http://xml.org/sax/features/namespaces"
+# true: Perform Namespace processing (default).
+# false: Optionally do not perform Namespace processing
+#        (implies namespace-prefixes).
+# access: (parsing) read-only; (not parsing) read/write
+
+feature_namespace_prefixes = "http://xml.org/sax/features/namespace-prefixes"
+# true: Report the original prefixed names and attributes used for Namespace
+#       declarations.
+# false: Do not report attributes used for Namespace declarations, and
+#        optionally do not report original prefixed names (default).
+# access: (parsing) read-only; (not parsing) read/write
+
+feature_string_interning = "http://xml.org/sax/features/string-interning"
+# true: All element names, prefixes, attribute names, Namespace URIs, and
+#       local names are interned using the built-in intern function.
+# false: Names are not necessarily interned, although they may be (default).
+# access: (parsing) read-only; (not parsing) read/write
+
+feature_validation = "http://xml.org/sax/features/validation"
+# true: Report all validation errors (implies external-general-entities and
+#       external-parameter-entities).
+# false: Do not report validation errors.
+# access: (parsing) read-only; (not parsing) read/write
+
+feature_external_ges = "http://xml.org/sax/features/external-general-entities"
+# true: Include all external general (text) entities.
+# false: Do not include external general entities.
+# access: (parsing) read-only; (not parsing) read/write
+
+feature_external_pes = "http://xml.org/sax/features/external-parameter-entities"
+# true: Include all external parameter entities, including the external
+#       DTD subset.
+# false: Do not include any external parameter entities, even the external
+#        DTD subset.
+# access: (parsing) read-only; (not parsing) read/write
+
+all_features = [feature_namespaces,
+                feature_namespace_prefixes,
+                feature_string_interning,
+                feature_validation,
+                feature_external_ges,
+                feature_external_pes]
+
+
+#============================================================================
+#
+# CORE PROPERTIES
+#
+#============================================================================
+
+property_lexical_handler = "http://xml.org/sax/properties/lexical-handler"
+# data type: xml.sax.sax2lib.LexicalHandler
+# description: An optional extension handler for lexical events like comments.
+# access: read/write
+
+property_declaration_handler = "http://xml.org/sax/properties/declaration-handler"
+# data type: xml.sax.sax2lib.DeclHandler
+# description: An optional extension handler for DTD-related events other
+#              than notations and unparsed entities.
+# access: read/write
+
+property_dom_node = "http://xml.org/sax/properties/dom-node"
+# data type: org.w3c.dom.Node
+# description: When parsing, the current DOM node being visited if this is
+#              a DOM iterator; when not parsing, the root DOM node for
+#              iteration.
+# access: (parsing) read-only; (not parsing) read/write
+
+property_xml_string = "http://xml.org/sax/properties/xml-string"
+# data type: String
+# description: The literal string of characters that was the source for
+#              the current event.
+# access: read-only
+
+property_encoding = "http://www.python.org/sax/properties/encoding"
+# data type: String
+# description: The name of the encoding to assume for input data.
+# access: write: set the encoding, e.g. established by a higher-level
+#                protocol. May change during parsing (e.g. after
+#                processing a META tag)
+#         read:  return the current encoding (possibly established through
+#                auto-detection.
+# initial value: UTF-8
+#
+
+property_interning_dict = "http://www.python.org/sax/properties/interning-dict"
+# data type: Dictionary
+# description: The dictionary used to intern common strings in the document
+# access: write: Request that the parser uses a specific dictionary, to
+#                allow interning across different documents
+#         read:  return the current interning dictionary, or None
+#
+
+all_properties = [property_lexical_handler,
+                  property_dom_node,
+                  property_declaration_handler,
+                  property_xml_string,
+                  property_encoding,
+                  property_interning_dict]
diff --git a/Lib/xml/sax/saxutils.py b/Lib/xml/sax/saxutils.py
new file mode 100644
index 000000000..a69c7f762
--- /dev/null
+++ b/Lib/xml/sax/saxutils.py
@@ -0,0 +1,368 @@
+"""\
+A library of useful helper classes to the SAX classes, for the
+convenience of application and driver writers.
+"""
+
+import os, urllib.parse, urllib.request
+import io
+import codecs
+from . import handler
+from . import xmlreader
+
+def __dict_replace(s, d):
+    """Replace substrings of a string using a dictionary."""
+    for key, value in d.items():
+        s = s.replace(key, value)
+    return s
+
+def escape(data, entities={}):
+    """Escape &, <, and > in a string of data.
+
+    You can escape other strings of data by passing a dictionary as
+    the optional entities parameter.  The keys and values must all be
+    strings; each key will be replaced with its corresponding value.
+    """
+
+    # must do ampersand first
+    data = data.replace("&", "&amp;")
+    data = data.replace(">", "&gt;")
+    data = data.replace("<", "&lt;")
+    if entities:
+        data = __dict_replace(data, entities)
+    return data
+
+def unescape(data, entities={}):
+    """Unescape &amp;, &lt;, and &gt; in a string of data.
+
+    You can unescape other strings of data by passing a dictionary as
+    the optional entities parameter.  The keys and values must all be
+    strings; each key will be replaced with its corresponding value.
+    """
+    data = data.replace("&lt;", "<")
+    data = data.replace("&gt;", ">")
+    if entities:
+        data = __dict_replace(data, entities)
+    # must do ampersand last
+    return data.replace("&amp;", "&")
+
+def quoteattr(data, entities={}):
+    """Escape and quote an attribute value.
+
+    Escape &, <, and > in a string of data, then quote it for use as
+    an attribute value.  The \" character will be escaped as well, if
+    necessary.
+
+    You can escape other strings of data by passing a dictionary as
+    the optional entities parameter.  The keys and values must all be
+    strings; each key will be replaced with its corresponding value.
+    """
+    entities = entities.copy()
+    entities.update({'\n': '&#10;', '\r': '&#13;', '\t':'&#9;'})
+    data = escape(data, entities)
+    if '"' in data:
+        if "'" in data:
+            data = '"%s"' % data.replace('"', "&quot;")
+        else:
+            data = "'%s'" % data
+    else:
+        data = '"%s"' % data
+    return data
+
+
+def _gettextwriter(out, encoding):
+    if out is None:
+        import sys
+        return sys.stdout
+
+    if isinstance(out, io.TextIOBase):
+        # use a text writer as is
+        return out
+
+    if isinstance(out, (codecs.StreamWriter, codecs.StreamReaderWriter)):
+        # use a codecs stream writer as is
+        return out
+
+    # wrap a binary writer with TextIOWrapper
+    if isinstance(out, io.RawIOBase):
+        # Keep the original file open when the TextIOWrapper is
+        # destroyed
+        class _wrapper:
+            __class__ = out.__class__
+            def __getattr__(self, name):
+                return getattr(out, name)
+        buffer = _wrapper()
+        buffer.close = lambda: None
+    else:
+        # This is to handle passed objects that aren't in the
+        # IOBase hierarchy, but just have a write method
+        buffer = io.BufferedIOBase()
+        buffer.writable = lambda: True
+        buffer.write = out.write
+        try:
+            # TextIOWrapper uses this methods to determine
+            # if BOM (for UTF-16, etc) should be added
+            buffer.seekable = out.seekable
+            buffer.tell = out.tell
+        except AttributeError:
+            pass
+    return io.TextIOWrapper(buffer, encoding=encoding,
+                            errors='xmlcharrefreplace',
+                            newline='\n',
+                            write_through=True)
+
+class XMLGenerator(handler.ContentHandler):
+
+    def __init__(self, out=None, encoding="iso-8859-1", short_empty_elements=False):
+        handler.ContentHandler.__init__(self)
+        out = _gettextwriter(out, encoding)
+        self._write = out.write
+        self._flush = out.flush
+        self._ns_contexts = [{}] # contains uri -> prefix dicts
+        self._current_context = self._ns_contexts[-1]
+        self._undeclared_ns_maps = []
+        self._encoding = encoding
+        self._short_empty_elements = short_empty_elements
+        self._pending_start_element = False
+
+    def _qname(self, name):
+        """Builds a qualified name from a (ns_url, localname) pair"""
+        if name[0]:
+            # Per http://www.w3.org/XML/1998/namespace, The 'xml' prefix is
+            # bound by definition to http://www.w3.org/XML/1998/namespace.  It
+            # does not need to be declared and will not usually be found in
+            # self._current_context.
+            if 'http://www.w3.org/XML/1998/namespace' == name[0]:
+                return 'xml:' + name[1]
+            # The name is in a non-empty namespace
+            prefix = self._current_context[name[0]]
+            if prefix:
+                # If it is not the default namespace, prepend the prefix
+                return prefix + ":" + name[1]
+        # Return the unqualified name
+        return name[1]
+
+    def _finish_pending_start_element(self,endElement=False):
+        if self._pending_start_element:
+            self._write('>')
+            self._pending_start_element = False
+
+    # ContentHandler methods
+
+    def startDocument(self):
+        self._write('<?xml version="1.0" encoding="%s"?>\n' %
+                        self._encoding)
+
+    def endDocument(self):
+        self._flush()
+
+    def startPrefixMapping(self, prefix, uri):
+        self._ns_contexts.append(self._current_context.copy())
+        self._current_context[uri] = prefix
+        self._undeclared_ns_maps.append((prefix, uri))
+
+    def endPrefixMapping(self, prefix):
+        self._current_context = self._ns_contexts[-1]
+        del self._ns_contexts[-1]
+
+    def startElement(self, name, attrs):
+        self._finish_pending_start_element()
+        self._write('<' + name)
+        for (name, value) in attrs.items():
+            self._write(' %s=%s' % (name, quoteattr(value)))
+        if self._short_empty_elements:
+            self._pending_start_element = True
+        else:
+            self._write(">")
+
+    def endElement(self, name):
+        if self._pending_start_element:
+            self._write('/>')
+            self._pending_start_element = False
+        else:
+            self._write('</%s>' % name)
+
+    def startElementNS(self, name, qname, attrs):
+        self._finish_pending_start_element()
+        self._write('<' + self._qname(name))
+
+        for prefix, uri in self._undeclared_ns_maps:
+            if prefix:
+                self._write(' xmlns:%s="%s"' % (prefix, uri))
+            else:
+                self._write(' xmlns="%s"' % uri)
+        self._undeclared_ns_maps = []
+
+        for (name, value) in attrs.items():
+            self._write(' %s=%s' % (self._qname(name), quoteattr(value)))
+        if self._short_empty_elements:
+            self._pending_start_element = True
+        else:
+            self._write(">")
+
+    def endElementNS(self, name, qname):
+        if self._pending_start_element:
+            self._write('/>')
+            self._pending_start_element = False
+        else:
+            self._write('</%s>' % self._qname(name))
+
+    def characters(self, content):
+        if content:
+            self._finish_pending_start_element()
+            if not isinstance(content, str):
+                content = str(content, self._encoding)
+            self._write(escape(content))
+
+    def ignorableWhitespace(self, content):
+        if content:
+            self._finish_pending_start_element()
+            if not isinstance(content, str):
+                content = str(content, self._encoding)
+            self._write(content)
+
+    def processingInstruction(self, target, data):
+        self._finish_pending_start_element()
+        self._write('<?%s %s?>' % (target, data))
+
+
+class XMLFilterBase(xmlreader.XMLReader):
+    """This class is designed to sit between an XMLReader and the
+    client application's event handlers.  By default, it does nothing
+    but pass requests up to the reader and events on to the handlers
+    unmodified, but subclasses can override specific methods to modify
+    the event stream or the configuration requests as they pass
+    through."""
+
+    def __init__(self, parent = None):
+        xmlreader.XMLReader.__init__(self)
+        self._parent = parent
+
+    # ErrorHandler methods
+
+    def error(self, exception):
+        self._err_handler.error(exception)
+
+    def fatalError(self, exception):
+        self._err_handler.fatalError(exception)
+
+    def warning(self, exception):
+        self._err_handler.warning(exception)
+
+    # ContentHandler methods
+
+    def setDocumentLocator(self, locator):
+        self._cont_handler.setDocumentLocator(locator)
+
+    def startDocument(self):
+        self._cont_handler.startDocument()
+
+    def endDocument(self):
+        self._cont_handler.endDocument()
+
+    def startPrefixMapping(self, prefix, uri):
+        self._cont_handler.startPrefixMapping(prefix, uri)
+
+    def endPrefixMapping(self, prefix):
+        self._cont_handler.endPrefixMapping(prefix)
+
+    def startElement(self, name, attrs):
+        self._cont_handler.startElement(name, attrs)
+
+    def endElement(self, name):
+        self._cont_handler.endElement(name)
+
+    def startElementNS(self, name, qname, attrs):
+        self._cont_handler.startElementNS(name, qname, attrs)
+
+    def endElementNS(self, name, qname):
+        self._cont_handler.endElementNS(name, qname)
+
+    def characters(self, content):
+        self._cont_handler.characters(content)
+
+    def ignorableWhitespace(self, chars):
+        self._cont_handler.ignorableWhitespace(chars)
+
+    def processingInstruction(self, target, data):
+        self._cont_handler.processingInstruction(target, data)
+
+    def skippedEntity(self, name):
+        self._cont_handler.skippedEntity(name)
+
+    # DTDHandler methods
+
+    def notationDecl(self, name, publicId, systemId):
+        self._dtd_handler.notationDecl(name, publicId, systemId)
+
+    def unparsedEntityDecl(self, name, publicId, systemId, ndata):
+        self._dtd_handler.unparsedEntityDecl(name, publicId, systemId, ndata)
+
+    # EntityResolver methods
+
+    def resolveEntity(self, publicId, systemId):
+        return self._ent_handler.resolveEntity(publicId, systemId)
+
+    # XMLReader methods
+
+    def parse(self, source):
+        self._parent.setContentHandler(self)
+        self._parent.setErrorHandler(self)
+        self._parent.setEntityResolver(self)
+        self._parent.setDTDHandler(self)
+        self._parent.parse(source)
+
+    def setLocale(self, locale):
+        self._parent.setLocale(locale)
+
+    def getFeature(self, name):
+        return self._parent.getFeature(name)
+
+    def setFeature(self, name, state):
+        self._parent.setFeature(name, state)
+
+    def getProperty(self, name):
+        return self._parent.getProperty(name)
+
+    def setProperty(self, name, value):
+        self._parent.setProperty(name, value)
+
+    # XMLFilter methods
+
+    def getParent(self):
+        return self._parent
+
+    def setParent(self, parent):
+        self._parent = parent
+
+# --- Utility functions
+
+def prepare_input_source(source, base=""):
+    """This function takes an InputSource and an optional base URL and
+    returns a fully resolved InputSource object ready for reading."""
+
+    if isinstance(source, str):
+        source = xmlreader.InputSource(source)
+    elif hasattr(source, "read"):
+        f = source
+        source = xmlreader.InputSource()
+        if isinstance(f.read(0), str):
+            source.setCharacterStream(f)
+        else:
+            source.setByteStream(f)
+        if hasattr(f, "name") and isinstance(f.name, str):
+            source.setSystemId(f.name)
+
+    if source.getCharacterStream() is None and source.getByteStream() is None:
+        sysid = source.getSystemId()
+        basehead = os.path.dirname(os.path.normpath(base))
+        sysidfilename = os.path.join(basehead, sysid)
+        if os.path.isfile(sysidfilename):
+            source.setSystemId(sysidfilename)
+            f = open(sysidfilename, "rb")
+        else:
+            source.setSystemId(urllib.parse.urljoin(base, sysid))
+            f = urllib.request.urlopen(source.getSystemId())
+
+        source.setByteStream(f)
+
+    return source
diff --git a/Lib/xml/sax/xmlreader.py b/Lib/xml/sax/xmlreader.py
new file mode 100644
index 000000000..716f22840
--- /dev/null
+++ b/Lib/xml/sax/xmlreader.py
@@ -0,0 +1,380 @@
+"""An XML Reader is the SAX 2 name for an XML parser. XML Parsers
+should be based on this code. """
+
+from . import handler
+
+from ._exceptions import SAXNotSupportedException, SAXNotRecognizedException
+
+
+# ===== XMLREADER =====
+
+class XMLReader:
+    """Interface for reading an XML document using callbacks.
+
+    XMLReader is the interface that an XML parser's SAX2 driver must
+    implement. This interface allows an application to set and query
+    features and properties in the parser, to register event handlers
+    for document processing, and to initiate a document parse.
+
+    All SAX interfaces are assumed to be synchronous: the parse
+    methods must not return until parsing is complete, and readers
+    must wait for an event-handler callback to return before reporting
+    the next event."""
+
+    def __init__(self):
+        self._cont_handler = handler.ContentHandler()
+        self._dtd_handler = handler.DTDHandler()
+        self._ent_handler = handler.EntityResolver()
+        self._err_handler = handler.ErrorHandler()
+
+    def parse(self, source):
+        "Parse an XML document from a system identifier or an InputSource."
+        raise NotImplementedError("This method must be implemented!")
+
+    def getContentHandler(self):
+        "Returns the current ContentHandler."
+        return self._cont_handler
+
+    def setContentHandler(self, handler):
+        "Registers a new object to receive document content events."
+        self._cont_handler = handler
+
+    def getDTDHandler(self):
+        "Returns the current DTD handler."
+        return self._dtd_handler
+
+    def setDTDHandler(self, handler):
+        "Register an object to receive basic DTD-related events."
+        self._dtd_handler = handler
+
+    def getEntityResolver(self):
+        "Returns the current EntityResolver."
+        return self._ent_handler
+
+    def setEntityResolver(self, resolver):
+        "Register an object to resolve external entities."
+        self._ent_handler = resolver
+
+    def getErrorHandler(self):
+        "Returns the current ErrorHandler."
+        return self._err_handler
+
+    def setErrorHandler(self, handler):
+        "Register an object to receive error-message events."
+        self._err_handler = handler
+
+    def setLocale(self, locale):
+        """Allow an application to set the locale for errors and warnings.
+
+        SAX parsers are not required to provide localization for errors
+        and warnings; if they cannot support the requested locale,
+        however, they must raise a SAX exception. Applications may
+        request a locale change in the middle of a parse."""
+        raise SAXNotSupportedException("Locale support not implemented")
+
+    def getFeature(self, name):
+        "Looks up and returns the state of a SAX2 feature."
+        raise SAXNotRecognizedException("Feature '%s' not recognized" % name)
+
+    def setFeature(self, name, state):
+        "Sets the state of a SAX2 feature."
+        raise SAXNotRecognizedException("Feature '%s' not recognized" % name)
+
+    def getProperty(self, name):
+        "Looks up and returns the value of a SAX2 property."
+        raise SAXNotRecognizedException("Property '%s' not recognized" % name)
+
+    def setProperty(self, name, value):
+        "Sets the value of a SAX2 property."
+        raise SAXNotRecognizedException("Property '%s' not recognized" % name)
+
+class IncrementalParser(XMLReader):
+    """This interface adds three extra methods to the XMLReader
+    interface that allow XML parsers to support incremental
+    parsing. Support for this interface is optional, since not all
+    underlying XML parsers support this functionality.
+
+    When the parser is instantiated it is ready to begin accepting
+    data from the feed method immediately. After parsing has been
+    finished with a call to close the reset method must be called to
+    make the parser ready to accept new data, either from feed or
+    using the parse method.
+
+    Note that these methods must _not_ be called during parsing, that
+    is, after parse has been called and before it returns.
+
+    By default, the class also implements the parse method of the XMLReader
+    interface using the feed, close and reset methods of the
+    IncrementalParser interface as a convenience to SAX 2.0 driver
+    writers."""
+
+    def __init__(self, bufsize=2**16):
+        self._bufsize = bufsize
+        XMLReader.__init__(self)
+
+    def parse(self, source):
+        from . import saxutils
+        source = saxutils.prepare_input_source(source)
+
+        self.prepareParser(source)
+        file = source.getCharacterStream()
+        if file is None:
+            file = source.getByteStream()
+        buffer = file.read(self._bufsize)
+        while buffer:
+            self.feed(buffer)
+            buffer = file.read(self._bufsize)
+        self.close()
+
+    def feed(self, data):
+        """This method gives the raw XML data in the data parameter to
+        the parser and makes it parse the data, emitting the
+        corresponding events. It is allowed for XML constructs to be
+        split across several calls to feed.
+
+        feed may raise SAXException."""
+        raise NotImplementedError("This method must be implemented!")
+
+    def prepareParser(self, source):
+        """This method is called by the parse implementation to allow
+        the SAX 2.0 driver to prepare itself for parsing."""
+        raise NotImplementedError("prepareParser must be overridden!")
+
+    def close(self):
+        """This method is called when the entire XML document has been
+        passed to the parser through the feed method, to notify the
+        parser that there are no more data. This allows the parser to
+        do the final checks on the document and empty the internal
+        data buffer.
+
+        The parser will not be ready to parse another document until
+        the reset method has been called.
+
+        close may raise SAXException."""
+        raise NotImplementedError("This method must be implemented!")
+
+    def reset(self):
+        """This method is called after close has been called to reset
+        the parser so that it is ready to parse new documents. The
+        results of calling parse or feed after close without calling
+        reset are undefined."""
+        raise NotImplementedError("This method must be implemented!")
+
+# ===== LOCATOR =====
+
+class Locator:
+    """Interface for associating a SAX event with a document
+    location. A locator object will return valid results only during
+    calls to DocumentHandler methods; at any other time, the
+    results are unpredictable."""
+
+    def getColumnNumber(self):
+        "Return the column number where the current event ends."
+        return -1
+
+    def getLineNumber(self):
+        "Return the line number where the current event ends."
+        return -1
+
+    def getPublicId(self):
+        "Return the public identifier for the current event."
+        return None
+
+    def getSystemId(self):
+        "Return the system identifier for the current event."
+        return None
+
+# ===== INPUTSOURCE =====
+
+class InputSource:
+    """Encapsulation of the information needed by the XMLReader to
+    read entities.
+
+    This class may include information about the public identifier,
+    system identifier, byte stream (possibly with character encoding
+    information) and/or the character stream of an entity.
+
+    Applications will create objects of this class for use in the
+    XMLReader.parse method and for returning from
+    EntityResolver.resolveEntity.
+
+    An InputSource belongs to the application, the XMLReader is not
+    allowed to modify InputSource objects passed to it from the
+    application, although it may make copies and modify those."""
+
+    def __init__(self, system_id = None):
+        self.__system_id = system_id
+        self.__public_id = None
+        self.__encoding  = None
+        self.__bytefile  = None
+        self.__charfile  = None
+
+    def setPublicId(self, public_id):
+        "Sets the public identifier of this InputSource."
+        self.__public_id = public_id
+
+    def getPublicId(self):
+        "Returns the public identifier of this InputSource."
+        return self.__public_id
+
+    def setSystemId(self, system_id):
+        "Sets the system identifier of this InputSource."
+        self.__system_id = system_id
+
+    def getSystemId(self):
+        "Returns the system identifier of this InputSource."
+        return self.__system_id
+
+    def setEncoding(self, encoding):
+        """Sets the character encoding of this InputSource.
+
+        The encoding must be a string acceptable for an XML encoding
+        declaration (see section 4.3.3 of the XML recommendation).
+
+        The encoding attribute of the InputSource is ignored if the
+        InputSource also contains a character stream."""
+        self.__encoding = encoding
+
+    def getEncoding(self):
+        "Get the character encoding of this InputSource."
+        return self.__encoding
+
+    def setByteStream(self, bytefile):
+        """Set the byte stream (a Python file-like object which does
+        not perform byte-to-character conversion) for this input
+        source.
+
+        The SAX parser will ignore this if there is also a character
+        stream specified, but it will use a byte stream in preference
+        to opening a URI connection itself.
+
+        If the application knows the character encoding of the byte
+        stream, it should set it with the setEncoding method."""
+        self.__bytefile = bytefile
+
+    def getByteStream(self):
+        """Get the byte stream for this input source.
+
+        The getEncoding method will return the character encoding for
+        this byte stream, or None if unknown."""
+        return self.__bytefile
+
+    def setCharacterStream(self, charfile):
+        """Set the character stream for this input source. (The stream
+        must be a Python 2.0 Unicode-wrapped file-like that performs
+        conversion to Unicode strings.)
+
+        If there is a character stream specified, the SAX parser will
+        ignore any byte stream and will not attempt to open a URI
+        connection to the system identifier."""
+        self.__charfile = charfile
+
+    def getCharacterStream(self):
+        "Get the character stream for this input source."
+        return self.__charfile
+
+# ===== ATTRIBUTESIMPL =====
+
+class AttributesImpl:
+
+    def __init__(self, attrs):
+        """Non-NS-aware implementation.
+
+        attrs should be of the form {name : value}."""
+        self._attrs = attrs
+
+    def getLength(self):
+        return len(self._attrs)
+
+    def getType(self, name):
+        return "CDATA"
+
+    def getValue(self, name):
+        return self._attrs[name]
+
+    def getValueByQName(self, name):
+        return self._attrs[name]
+
+    def getNameByQName(self, name):
+        if name not in self._attrs:
+            raise KeyError(name)
+        return name
+
+    def getQNameByName(self, name):
+        if name not in self._attrs:
+            raise KeyError(name)
+        return name
+
+    def getNames(self):
+        return list(self._attrs.keys())
+
+    def getQNames(self):
+        return list(self._attrs.keys())
+
+    def __len__(self):
+        return len(self._attrs)
+
+    def __getitem__(self, name):
+        return self._attrs[name]
+
+    def keys(self):
+        return list(self._attrs.keys())
+
+    def __contains__(self, name):
+        return name in self._attrs
+
+    def get(self, name, alternative=None):
+        return self._attrs.get(name, alternative)
+
+    def copy(self):
+        return self.__class__(self._attrs)
+
+    def items(self):
+        return list(self._attrs.items())
+
+    def values(self):
+        return list(self._attrs.values())
+
+# ===== ATTRIBUTESNSIMPL =====
+
+class AttributesNSImpl(AttributesImpl):
+
+    def __init__(self, attrs, qnames):
+        """NS-aware implementation.
+
+        attrs should be of the form {(ns_uri, lname): value, ...}.
+        qnames of the form {(ns_uri, lname): qname, ...}."""
+        self._attrs = attrs
+        self._qnames = qnames
+
+    def getValueByQName(self, name):
+        for (nsname, qname) in self._qnames.items():
+            if qname == name:
+                return self._attrs[nsname]
+
+        raise KeyError(name)
+
+    def getNameByQName(self, name):
+        for (nsname, qname) in self._qnames.items():
+            if qname == name:
+                return nsname
+
+        raise KeyError(name)
+
+    def getQNameByName(self, name):
+        return self._qnames[name]
+
+    def getQNames(self):
+        return list(self._qnames.values())
+
+    def copy(self):
+        return self.__class__(self._attrs, self._qnames)
+
+
+def _test():
+    XMLReader()
+    IncrementalParser()
+    Locator()
+
+if __name__ == "__main__":
+    _test()