SQLAlchemy Generic Relationship simple example

I know similar questions have been asked, however I am really struggling to understand how generic fields are implemented in SQLAlchemy.

I have a Permissions class/table which I want to contain a field which can relate to any model type.

I have looked at the examples and this blog post http://techspot.zzzeek.org/2007/05/29/polymorphic-associations-with-sqlalchemy/

Is it possible to have a generic relation without a separate table? Just by storing the object_type and id? Something along these lines:

class Permission(AbstractBase):
    user = relationship("User", backref=backref('permissions'))
    permission_type = column(String())
    object = #The object the permission applies to, could be any type.

I guess just a really simple example would be appreciated!

Also, it's worth noting I am coming from a Django background!

Thanks