def assertSessionProvidesISession(self):
        """
        self.session.session should provide I{ISession}.
        """
        self.assertTrue(session.ISession.providedBy(self.session.session),
                        "ISession not provided by %r" % self.session.session)

        self.session.session should provide I{ISession}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_session.py