@base.resource(relationships.FollowedBy)
    def followed_by(self):
        return relationships.FollowedBy(self)
The backend is this module itself.
dataset/ETHPy150Open ducksboard/libsaas/libsaas/services/instagram/users.py/User.followed_by--crossover with--dataset/ETHPy150Open openstack/ec2-api/ec2api/db/sqlalchemy/api.py/get_backend