def check_etag_header(self):
        etag = self._headers.get("Etag")
        inm = utf8(self.request.headers.get("If-None-Match", ""))
        return bool(etag and inm and inm.find(etag) >= 0)
Checks the ``Etag`` header against requests's ``If-None-Match``.
dataset/ETHPy150Open RobotWebTools/rosbridge_suite/rosbridge_server/src/tornado/web.py/RequestHandler.check_etag_header