code: def _get_item(self, question_id):
          
          question_map = self._get_question_map(question_id)  # Throws NotFound()
          real_question_id = Id(question_map['questionId'])
          return self._get_item_lookup_session().get_item(real_question_id)
docs: we need a middle-man method to convert the unique "assessment-session"
              authority question_ids into "real" itemIds
          BUT this also has to return the "magic" item, so we can't rely
          on
                  question = self.get_question(question_id)
                  ils = self._get_item_lookup_session()
                  return ils.get_item(Id(question._my_map['itemId']))