class FooCycle(Base):
    __tablename__ = 'foocycle'
foo_id = Column(String(50), ForeignKey('foo.id'), primary_key=True)
some_number = Column(Integer, primary_key=True)
foo = relationship('Foo', backref=backref('cycles', cascade=
    'save-update, merge, delete, delete-orphan'))
Dependency rule tried to blank out primary key in SQLAlchemy, when foreign key constraint is part of composite primary key