def test_deferredResult(self):
        """
        L{threads.deferToThreadPool} executes the function passed, and
        correctly handles the positional and keyword arguments given.
        """
        d = threads.deferToThreadPool(reactor, self.tp,
                                      lambda x, y=5: x + y, 3, y=4)
        d.addCallback(self.assertEqual, 7)
        return d

        L{threads.deferToThreadPool} executes the function passed, and
        correctly handles the positional and keyword arguments given.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_threads.py