code: def _warn_if_string(iterable):
      
      if isinstance(iterable, string_types):
          from warnings import warn
          warn(Warning('response iterable was set to a string.  This appears '
                       'to work but means that the server will send the '
                       'data to the client char, by char.  This is almost '
                       'never intended behavior, use response.data to assign '
                       'strings to the response object.'), stacklevel=2)
docs: Helper for the response objects to check if the iterable returned
      to the WSGI server is not a string.