methods.py

for endpoint in ModelView.__subclasses__():
        def relationships(self, id):
            print id

        for key in endpoint.model.__dict__:
            if key.endswith('_id'):
                setattr(endpoint, 'related_%s' % (key), types.MethodType(
                    route(
                        rule='/<id>/related_%s' % (key),
                        endpoint='related_%s' % (key),
                        methods=['GET']
                    )(relationships), None, endpoint
                ))

        endpoint.register(app, route_prefix='/v1/')