code: def _get_tokens_dict(self):
          
          if self._tokens_dict is None:
              tokens = [Token(element) for element in self._element.xpath('tokens/token')]
              self._tokens_dict = OrderedDict([(t.id, t) for t in tokens])
          return self._tokens_dict
docs: Accesses tokens dict
  
          :return: The ordered dict of the tokens
          :rtype: collections.OrderedDict