SQLA dynamic hybrid property trouble

# -*- coding: utf-8 -*-

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.ext.hybrid import hybrid_property, hybrid_method
from sqlalchemy import Column, Integer, ForeignKey, String

sa_engine = create_engine("sqlite:///:memory:")
Session = sessionmaker(bind=sa_engine)
s = Session()

class Base(object):
    @declared_attr
    def __tablename__(cls):
        return cls.__name__.lower()
    id = Column(Integer, primary_key=True)

Base = declarative_base(cls=Base)

class Order(Base):
    number = Column(String(5))

class Invoice(Base):
    number = Column(String(5))

class Payable(Base):

    type = Column(String(50))

    order_id = Column(Integer, ForeignKey('order.id'))
    order = relationship(Order)

    invoice_id = Column(Integer, ForeignKey('invoice.id'))
    invoice = relationship(Invoice)

    def __init__(self, val, str_type):
        self.type = str_type.lower()
        setattr(self, self.type, val)

    def __repr__(self):
        return 'Type:{}'.format(self.type)

    @hybrid_property
    def value(self):
        return getattr(self, self.type)


Base.metadata.create_all(sa_engine)

order = Order()
invoice = Invoice()
invoice.number = '00001'

pbl1 = Payable(invoice, 'Invoice')
pbl2 = Payable(order, 'Order')

s.add(invoice)
s.add(order)
s.add(pbl1)
s.add(pbl2)

s.commit()
print(pbl1.value.number) #this works
res = s.query(Payable).filter(Payable.type=='order').all() #this works
res = s.query(Payable).filter(Payable.order==order).all() #this works too
res = s.query(Payable).filter(Payable.value==order).all() #this does not