code: def get_group_member_ids(self, group_id, start=None, timeout=None):
          
          params = None if start is None else {'start': start}
  
          response = self._get(
              '/v2/bot/group/{group_id}/members/ids'.format(group_id=group_id),
              params=params,
              timeout=timeout
          )
  
          return MemberIds.new_from_json_dict(response.json)
docs: Call get group member IDs API.
  
          https://devdocs.line.me/en/#get-group-room-member-ids
  
          Gets the user IDs of the members of a group that the bot is in.
          This includes the user IDs of users who have not added the bot as a friend
          or has blocked the bot.
  
          :param str group_id: Group ID
          :param str start: continuationToken
          :param timeout: (optional) How long to wait for the server
              to send data before giving up, as a float,
              or a (connect timeout, read timeout) float tuple.
              Default is self.http_client.timeout
          :type timeout: float | tuple(float, float)
          :rtype: :py:class:`linebot.models.responses.MemberIds`
          :return: MemberIds instance