code: def _subtoken_ids_to_tokens(self, subtokens):
      
      concatenated = "".join(
          [self._subtoken_id_to_subtoken_string(s) for s in subtokens])
      split = concatenated.split("_")
      ret = []
      for t in split:
        if t:
          unescaped = _unescape_token(t + "_")
          if unescaped:
            ret.append(unescaped)
      return ret
docs: Converts a list of subtoken ids to a list of tokens.
  
      Args:
        subtokens: a list of integers in the range [0, vocab_size)
      Returns:
        a list of strings.