docs: def _write(self, lines, fname):
          """
          Writes a intermediate temporary sorted file
  
          :param lines: The lines to write.
          :param fname: The name of the temporary file.
          :return:
          """
          with open(fname, 'wb') as out_fhndl:
              for line in sorted(lines, key=self.key):
                  pickle.dump(line, out_fhndl)