def test_returnsListOfICiphers(self):
        """
        L{sslverify._expandCipherString} always returns a L{list} of
        L{interfaces.ICipher}.
        """
        ciphers = sslverify._expandCipherString(u'ALL', SSL.SSLv23_METHOD, 0)
        self.assertIsInstance(ciphers, list)
        bogus = []
        for c in ciphers:
            if not interfaces.ICipher.providedBy(c):
                bogus.append(c)

        self.assertEqual([], bogus)

        L{sslverify._expandCipherString} always returns a L{list} of
        L{interfaces.ICipher}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sslverify.py