code: func RegisterShhService(stack *node.Node, cfg *whisper.Config) {
  	if err := stack.Register(func(n *node.ServiceContext) (node.Service, error) {
  		return whisper.New(cfg), nil
  	}); err != nil {
  		Fatalf("Failed to register the Whisper service: %v", err)
  	}
  }
docs: // RegisterShhService configures Whisper and adds it to the given node.