docs: def _to_gzipfile(self, file_generator):
          """Convert file to gzip-compressed file.
          :return: None
          :rtype: :py:obj:`None`
          """
          with gzip.GzipFile(file_generator.to_path, mode="wb") as outfile:
              for f in file_generator:
                  outfile.write(f.writestr(file_generator.to_format).encode())