code: def add(self, *obj_or_objs):
          
          objs = obj_or_objs
          if not isinstance(obj_or_objs, (list, tuple)):
              objs = (obj_or_objs, )
          change = operation.Relation(objs, ())
          self.parent.set(self.key, change)
          self.target_class_name = change._target_class_name
docs: 添加一个新的 leancloud.Object 至 Relation。
  
          :param obj_or_objs: 需要添加的对象或对象列表