def detach(self) -> iostream.IOStream:
        """Take control of the underlying stream.

        Returns the underlying `.IOStream` object and stops all
        further HTTP processing. Intended for implementing protocols
        like websockets that tunnel over an HTTP handshake.

        This method is only supported when HTTP/1.1 is used.

        .. versionadded:: 5.1
        """
        self._finished = True
        # TODO: add detach to HTTPConnection?
        return self.request.connection.detach()