def test_peerFromSSLTransport(self):
        """
        Verify that peerFromTransport successfully creates the correct
        certificate if passed a valid SSL transport.
        """
        self.assertEqual(
            sslverify.Certificate.peerFromTransport(
                _ActualSSLTransport()).serialNumber(),
            12346)

        Verify that peerFromTransport successfully creates the correct
        certificate if passed a valid SSL transport.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sslverify.py