class Foo(Base):
    __tablename__ = 'foo'
id = Column(Integer, primary_key=True)
bar_id = Column(Integer, ForeignKey('bar.id'))
bar = relationship('Bar')


class Bar(Base):
    __tablename__ = 'bar'
id = Column(Integer, primary_key=True)

@hybrid_property
def foo_count(self):
    pass
SQLAlchemy - How can I make eager loading count property