added doc-strings

cpp/src/arrow/buffer.h

@@ -89,6 +89,8 @@ class ARROW_EXPORT Buffer {
 
   bool is_mutable() const { return is_mutable_; }
 
+  /// \brief Construct a new std::string with a hexadecimal representation of the buffer.
+  /// \return std::string
   std::string ToHexString();
 
   /// Return true if both buffers are the same size and contain the same bytes

python/pyarrow/io.pxi

@@ -869,6 +869,13 @@ cdef class Buffer:
         return <uintptr_t> self.buffer.get().data()
 
     def hex(self):
+        """
+        Compute hexadecimal representation of the buffer.
+
+        Returns
+        -------
+        : bytes
+        """
         return self.buffer.get().ToHexString()
 
     @property