def test_removeHeaderDoesntExist(self):
        """
        L{Headers.removeHeader} is a no-operation when the specified header is
        not found.
        """
        h = Headers()
        h.removeHeader(u"test")
        self.assertEqual(list(h.getAllRawHeaders()), [])

        L{Headers.removeHeader} is a no-operation when the specified header is
        not found.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_http_headers.py