fix flake8 linting

python/pyarrow/tests/test_serialization.py

@@ -88,6 +88,7 @@ def array_custom_serializer(obj):
 def array_custom_deserializer(serialized_obj):
     return np.array(serialized_obj[0], dtype=np.dtype(serialized_obj[1]))
 
+
 pa.lib.register_type(np.ndarray, 20 * b"\x00", pickle=False,
                      custom_serializer=array_custom_serializer,
                      custom_deserializer=array_custom_deserializer)