def test_allowedAnonymousClientConnection(self):
        """
        Check that anonymous connections are allowed when certificates aren't
        required on the server.
        """
        onData = defer.Deferred()
        self.loopback(sslverify.OpenSSLCertificateOptions(privateKey=self.sKey,
                            certificate=self.sCert, requireCertificate=False),
                      sslverify.OpenSSLCertificateOptions(
                          requireCertificate=False),
                      onData=onData)

        return onData.addCallback(
            lambda result: self.assertEqual(result, WritingProtocol.byte))

        Check that anonymous connections are allowed when certificates aren't
        required on the server.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sslverify.py