code: def mentions(self):
          
          if self._mentions is None:
              self._mentions = []
              for mention_element in self._element.xpath('mention'):
                  this_mention = Mention(self, mention_element)
                  self._mentions.append(this_mention)
                  if this_mention.representative:
                      self._representative = this_mention
          return self._mentions
docs: Returns mentions
  
          :return: list of mentions
          :rtype: list