def test_getHandle(self):
        """
        L{TLSMemoryBIOProtocol.getHandle} returns the L{OpenSSL.SSL.Connection}
        instance it uses to actually implement TLS.

        This may seem odd.  In fact, it is.  The L{OpenSSL.SSL.Connection} is
        not actually the "system handle" here, nor even an object the reactor
        knows about directly.  However, L{twisted.internet.ssl.Certificate}'s
        C{peerFromTransport} and C{hostFromTransport} methods depend on being
        able to get an L{OpenSSL.SSL.Connection} object in order to work
        properly.  Implementing L{ISystemHandle.getHandle} like this is the
        easiest way for those APIs to be made to work.  If they are changed,
        then it may make sense to get rid of this implementation of
        L{ISystemHandle} and return the underlying socket instead.
        """
        factory = ClientFactory()
        contextFactory = ClientTLSContext()
        wrapperFactory = TLSMemoryBIOFactory(contextFactory, True, factory)
        proto = TLSMemoryBIOProtocol(wrapperFactory, Protocol())
        transport = StringTransport()
        proto.makeConnection(transport)
        self.assertIsInstance(proto.getHandle(), ConnectionType)

        L{TLSMemoryBIOProtocol.getHandle} returns the L{OpenSSL.SSL.Connection}
        instance it uses to actually implement TLS.

        This may seem odd.  In fact, it is.  The L{OpenSSL.SSL.Connection} is
        not actually the "system handle" here, nor even an object the reactor
        knows about directly.  However, L{twisted.internet.ssl.Certificate}'s
        C{peerFromTransport} and C{hostFromTransport} methods depend on being
        able to get an L{OpenSSL.SSL.Connection} object in order to work
        properly.  Implementing L{ISystemHandle.getHandle} like this is the
        easiest way for those APIs to be made to work.  If they are changed,
        then it may make sense to get rid of this implementation of
        L{ISystemHandle} and return the underlying socket instead.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/test/test_tls.py