if m.handlers.hasSubhandler(subID) && !id.isTestHandler() {
		return fmt.Errorf("handler %v, subroute:%v: %w", id.String(), s, ErrHandlerAlreadyExists)
	}
	m.handlers.subSingle[subID] = h
	// Copy so clients can also pick it up for other subpaths.
	m.handlers.subSingle[makeZeroSubHandlerID(id)] = h
	return nil
}

/*
// RegisterStateless will register a stateless handler that serves

	single    [handlerLast]SingleHandlerFn
	stateless [handlerLast]*StatelessHandler
	streams   [handlerLast]*StreamHandler

	subSingle    map[subHandlerID]SingleHandlerFn
	subStateless map[subHandlerID]*StatelessHandler
	subStreams   map[subHandlerID]*StreamHandler
}

func (h *handlers) init() {
	h.subSingle = make(map[subHandlerID]SingleHandlerFn)
	h.subStateless = make(map[subHandlerID]*StatelessHandler)

		fmt.Println(m.MuxID, c.StringReverse(), "INCOMING")
	}
	// Singleshot message
	var handler SingleHandlerFn
	if subID == nil {
		handler = c.handlers.single[m.Handler]
	} else {
		handler = c.handlers.subSingle[*subID]
	}
	if handler == nil {
		gridLogIf(ctx, c.queueMsg(m, muxConnectError{Error: "Invalid Handler for type"}))
		return
	}