          """
          Init this serializer given a stream or a string
          """
          self.options = options
          if isinstance(stream_or_string, six.string_types):
              self.stream = six.StringIO(stream_or_string)
          else:
              self.stream = stream_or_string
  
      def __iter__(self):
 
</s> remove     if isinstance(stream_or_string, six.string_types):
 </s> add     if isinstance(stream_or_string, str): </s> remove     if not isinstance(stream_or_string, (bytes, six.string_types)):
 </s> add     if not isinstance(stream_or_string, (bytes, str)): </s> remove     if isinstance(file_h, six.string_types):
 </s> add     if isinstance(file_h, str): </s> remove     if isinstance(data_source, six.string_types):
 </s> add     if isinstance(data_source, str): </s> remove         if isinstance(instance._regex, six.string_types):
 </s> add         if isinstance(instance._regex, str):
        if isinstance(stream_or_string, str):
          """
          Init this serializer given a stream or a string
          """
          self.options = options
        if isinstance(stream_or_string, str):
              self.stream = six.StringIO(stream_or_string)
          else:
              self.stream = stream_or_string
  
      def __iter__(self):
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews. 
django/core/serializers/base.py