SQLAlchemy One-to-Many relationship on single table inheritance - declarative

Basically, I have this model, where I mapped in a single table a "BaseNode" class, and two subclasses. The point is that I need one of the subclasses, to have a one-to-many relationship with the other subclass. So in sort, it is a relationship with another row of different class (subclass), but in the same table. How do you think I could write it using declarative syntax?.

Note: Due to other relationships in my model, if it is possible, I really need to stick with single table inheritance.

class BaseNode(DBBase):
    __tablename__ = 'base_node'
    id = Column(Integer, primary_key=True)
    discriminator = Column('type', String(50))
    __mapper_args__ = {'polymorphic_on': discriminator}

class NodeTypeA(BaseNode):
    __mapper_args__ = {'polymorphic_identity': 'NodeTypeA'}
    typeB_children = relationship('NodeTypeB', backref='parent_node')


class NodeTypeB(BaseNode):
    __mapper_args__ = {'polymorphic_identity': 'NodeTypeB'}
    parent_id = Column(Integer, ForeignKey('base_node.id'))

Using this code will throw:

sqlalchemy.exc.ArgumentError: NodeTypeA.typeB_children and back-reference NodeTypeB.parent_node are both of the same direction . Did you mean to set remote_side on the many-to-one side ?

Any ideas or suggestions?