def find_handler(
        self, request: httputil.HTTPServerRequest, **kwargs: Any
    ) -> Optional[httputil.HTTPMessageDelegate]:
        """Must be implemented to return an appropriate instance of `~.httputil.HTTPMessageDelegate`
        that can serve the request.
        Routing implementations may pass additional kwargs to extend the routing logic.

        :arg httputil.HTTPServerRequest request: current HTTP request.
        :arg kwargs: additional keyword arguments passed by routing implementation.
        :returns: an instance of `~.httputil.HTTPMessageDelegate` that will be used to
            process the request.
        """
        raise NotImplementedError()