<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _warn_if_string(iterable):
 """Helper for the response objects to check if the iterable returned to the WSGI server is not a string. """

    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)