def test_requestMethodIsNativeString(self):
        """
        The C{'REQUEST_METHOD'} key of the C{environ} C{dict} passed to the
        application is always a native string.
        """
        for method in b"GET", u"GET":
            request, result = self.prepareRequest()
            request.requestReceived(method)
            result.addCallback(self.environKeyEqual('REQUEST_METHOD', 'GET'))
            self.assertIsInstance(self.successResultOf(result), str)

        The C{'REQUEST_METHOD'} key of the C{environ} C{dict} passed to the
        application is always a native string.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_wsgi.py