def test_async(self):
        """
        Call an asynchronous method of a L{util.LocalAsRemote} object and check
        the result.
        """
        o = LocalRemoteTest()
        o = LocalRemoteTest()
        d = o.callRemote("add", 2, y=4)
        self.assertIsInstance(d, Deferred)
        d.addCallback(self.assertEqual, 6)
        return d

        Call an asynchronous method of a L{util.LocalAsRemote} object and check
        the result.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/test/test_pb.py