Python 检查ponyorm是否存在PrimaryKey

我正在尝试使用小马orm来查看是否存在主键。我走了这么远，但总是出错

class Favorite(db.Entity):
    game = Required(Game)
    user = Required(User)
    date_favorited = Required(datetime)
    PrimaryKey(user, game)

下面是函数

    if Favorite.get(lambda: user, game) is not None:
        favorited = 1

这是errro

TypeError: The second positional arguments should be globals dictionary. Got: Game[12]

他在医院里得到了帮助

if Favorite.exists(user=x, game=y):
    favorited = 1