Resets all headers and content for this response.

def clear(self) -> None:
        """Resets all headers and content for this response."""
        self._headers = httputil.HTTPHeaders(
            {
                "Server": "TornadoServer/%s" % tornado.version,
                "Content-Type": "text/html; charset=UTF-8",
                "Date": httputil.format_timestamp(time.time()),
            }
        )
        self.set_default_headers()
        self._write_buffer = []  # type: List[bytes]
        self._status_code = 200
        self._reason = httputil.responses[200]