def METHOD_NAME(talk_room_list):
    """
    returns :talk toom 的时间range 以及最早和最晚的时间
    int, datetime.time, datetime.time
    """
    t_start = talk_room_list[0].Rstart
    t_finish = talk_room_list[0].Rfinish
    for room in talk_room_list:
        t_start = min(t_start, room.Rstart)
        t_finish = max(t_finish, room.Rfinish)
    return t_start, t_finish