SQLAlchemy joined table inheritance and mixins

dump.sql

PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE node (
	id INTEGER NOT NULL, -- from Mixin
	name VARCHAR(200), -- from Mixin
	published BOOLEAN NOT NULL, 
	type VARCHAR(20), 
	title VARCHAR(200), -- from Mixin
	PRIMARY KEY (id), 
	CHECK (published IN (0, 1))
);
CREATE TABLE page (
	name VARCHAR(200), -- from Mixin, but shouldn't be here
	id INTEGER NOT NULL, -- from Page
	content TEXT, 
	PRIMARY KEY (id),
	FOREIGN KEY(id) REFERENCES node (id) -- from Page
);
COMMIT;

sqla-inheritance.py

from sqlalchemy import Column, Unicode, Integer, Boolean, Text, ForeignKey, create_engine
from sqlalchemy.ext.declarative import declarative_base, declared_attr

Base = declarative_base()


class Mixin(object):
    id = Column(Integer, primary_key=True)
    name = Column(Unicode(200))

    @declared_attr
    def title(cls):
        return Column(Unicode(200))


class Node(Mixin, Base):
    __tablename__ = 'node'
    published = Column(Boolean, nullable=False, default=False)
    type = Column(Unicode(20))
    __mapper_args__ = {'polymorphic_on': type, 'polymorphic_identity': 'node'}


class Page(Node):
    __tablename__ = 'page'
    id = Column(Integer, ForeignKey('node.id'), primary_key=True, nullable=False)
    content = Column(Text)
    __mapper_args__ = {'polymorphic_identity': 'page'}


if __name__ == '__main__':
    engine = create_engine('sqlite:///test.db')
    Base.metadata.create_all(engine)
    import os
    os.system("echo .dump | sqlite3 test.db")