code: def list(self, before_id=None, since_id=None, after_id=None, limit=20):
          
          return pagers.MessageList(self, self._raw_list, before_id=before_id,
                                    after_id=after_id, since_id=since_id,
                                    limit=limit)
docs: Return a page of group messages.
  
          The messages come in reversed order (newest first). Note you can only
          provide _one_ of ``before_id``, ``since_id``, or ``after_id``.
  
          :param str before_id: message ID for paging backwards
          :param str after_id: message ID for paging forwards
          :param str since_id: message ID for most recent messages since
          :param int limit: maximum number of messages per page
          :return: group messages
          :rtype: :class:`~groupy.pagers.MessageList`