def render(self, request):
        """
        Leave the request open for future writes.
        """
        self.request = request
        if request.method not in self.allowedMethods:
            raise error.UnsupportedMethod(self.allowedMethods)
        self.request.write(b"some data")
        return server.NOT_DONE_YET

        Leave the request open for future writes.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_web.py