def test_stopProxyingUnreferencesProducer(self):
        transport = StringTransport()
        proxy = TransportProxyProducer(transport)
        self.assertIdentical(proxy._producer, transport)
        proxy._stopProxying()
        self.assertIdentical(proxy._producer, None)
L{TransportProxyProducer._stopProxying} drops the reference to the
dataset/ETHPy150Open twisted/twisted/twisted/web/test/test_newclient.py/TransportProxyProducerTests.test_stopProxyingUnreferencesProducer