def test_getHeader(self):
        """
        L{http.Request.getHeader} returns the value of the named request
        header.
        """
        req = http.Request(DummyChannel(), False)
        req.requestHeaders.setRawHeaders(b"test", [b"lemur"])
        self.assertEqual(req.getHeader(b"test"), b"lemur")

        L{http.Request.getHeader} returns the value of the named request
        header.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_http.py