code: def _split(self, iterator, tmp_dir):
          fnames = []
          for i, lines in enumerate(iterator):
              lines = list(lines)
              out_fname = os.path.join(tmp_dir, self.TMP_FNAME.format(i + 1))
              self._write(lines, out_fname)
              fnames.append(out_fname)
              if len(lines) < self.max_lines:
                  break
          return fnames