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