code: def _token_to_subtoken_ids(self, token):
      
      cache_location = hash(token) % self._cache_size
      cache_key, cache_value = self._cache[cache_location]
      if cache_key == token:
        return cache_value
      ret = self._escaped_token_to_subtoken_ids(
          _escape_token(token, self._alphabet))
      self._cache[cache_location] = (token, ret)
      return ret
docs: Converts token to a list of subtoken ids.
  
      Args:
        token: a string.
      Returns:
        a list of integers in the range [0, vocab_size)