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

        L{threads.deferToThread} 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