python - SQLAlchemy-Utils 聚合 CompositeType

Question

StatType = CompositeType(
    'stat',
    [
        Column('home', Integer),
        Column('guest', Integer)
    ]
    )

CardType = CompositeType(
    'cards',
    [
        Column('yellow', StatType),
        Column('red', StatType)
    ]
    )

class Referee(Base):
    __tablename__ = 'Referee'

    id = Column(Integer, primary_key=True)
    matches = relationship("FootballMatch", back_populates="referee")

    name = Column(String, unique=True)

    @aggregated('avg_red', Column(Numeric))
    def avg_red(self):
        return func.avg(FootballMatch.cards.red.home + FootballMatch.cards.red.guest)

    @aggregated('avg_yellow', Column(Numeric))
    def avg_yellow(self):
        return func.avg(FootballMatch.cards.yellow.home + FootballMatch.cards.yellow.guest)

我正在使用带有 Postgres 的 sqlalchemy-Utils。这个想法很简单，我想汇总裁判每场比赛的平均牌数。但我得到了例外：

Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with FootballMatch.cards has an attribute 'red'

这样的事情可能吗？