code: def _add_message_info_multiple(self, msg_info):
          
          if msg_info.key in self._msg_info_multiple_dict:
              if msg_info.is_continued:
                  self._msg_info_multiple_dict[msg_info.key][-1].append(msg_info.value)
              else:
                  self._msg_info_multiple_dict[msg_info.key].append([msg_info.value])
          else:
              self._msg_info_multiple_dict[msg_info.key] = [[msg_info.value]]
docs: add a message info multiple to self._msg_info_multiple_dict