def test_stopProducingSetsRequestToNone(self):
        """
        L{StaticProducer.stopProducing} sets the request instance variable to
        None, which indicates to subclasses' resumeProducing methods that no
        more data should be produced.
        """
        fileObject = StringIO()
        producer = static.StaticProducer(DummyRequest([]), fileObject)
        producer.stopProducing()
        self.assertIdentical(None, producer.request)

        L{StaticProducer.stopProducing} sets the request instance variable to
        None, which indicates to subclasses' resumeProducing methods that no
        more data should be produced.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_static.py