docs: 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))