Python TurboGears:sqlalchemy.exc.ArgumentAdmin crud中存在错误

如果我将自动crud用于管理部分，有时，当我尝试创建/编辑某些对象时，我会出现以下错误：

sqlalchemy.exc.ArgumentError: Class object expected, got '<bound method _class_resolver._resolve_name of <sqlalchemy.ext.declarative.clsregistry._class_resolver object at 0x7f2aba659860>>'.

class User(DeclarativeBase):
    __tablename__ = 'tg_user'

    user_id = Column(Integer, autoincrement=True, primary_key=True)
    user_name = Column(Unicode(16), unique=True, nullable=False)
    email_address = Column(Unicode(255), unique=True, nullable=False)
    display_name = Column(Unicode(255))
    _password = Column('password', Unicode(128))
    created = Column(DateTime, default=datetime.now)

    tg_player_id = Column(Integer, ForeignKey('player.player_id'))
    player = relationship("Player", backref='tg_user')


class Player(DeclarativeBase):

    __tablename__ = 'player'

    player_id = Column(Integer, primary_key=True, nullable=False)
    player_tg_id = Column(Unicode(30))
    username = Column(Unicode(100))