def test_interfacesForTransport(self):
        """
        If the protocol objects returned by the factory given to
        L{ClientService} provide special "marker" interfaces for their
        transport - L{IHalfCloseableProtocol} or L{IFileDescriptorReceiver} -
        those interfaces will be provided by the protocol objects passed on to
        the reactor.
        """
        @implementer(IHalfCloseableProtocol, IFileDescriptorReceiver)
        class FancyProtocol(Protocol, object):
            """
            Provider of various interfaces.
            """
        cq, service = self.makeReconnector(protocolType=FancyProtocol)
        reactorFacing = cq.constructedProtocols[0]
        self.assertTrue(IFileDescriptorReceiver.providedBy(reactorFacing))
        self.assertTrue(IHalfCloseableProtocol.providedBy(reactorFacing))

        If the protocol objects returned by the factory given to
        L{ClientService} provide special "marker" interfaces for their
        transport - L{IHalfCloseableProtocol} or L{IFileDescriptorReceiver} -
        those interfaces will be provided by the protocol objects passed on to
        the reactor.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/test/test_internet.py