Return ``True`` if GS standalone folder object.

        GS will create a 0 byte ``<FOLDER NAME>_$folder$`` key as a
        pseudo-directory place holder if there are no files present.

def _is_gs_folder(cls, result):
        """Return ``True`` if GS standalone folder object.

        GS will create a 0 byte ``<FOLDER NAME>_$folder$`` key as a
        pseudo-directory place holder if there are no files present.
        """
        return (cls.is_key(result) and
                result.size == 0 and
                result.name.endswith(cls._gs_folder_suffix))