code: func (p *PushCenter) RegisterHandlerForIdentity(handler EventHandler, identity Identity) {
  
  	if identity.Name == AllIdentity.Name {
  		p.defaultHander = handler
  		return
  	}
  
  	p.handlers[identity.Name] = handler
  }
docs: // RegisterHandlerForIdentity registers the given EventHandler for the given Entity Identity.
  // You can pass the bambou.AllIdentity as identity to register the handler
  // for all events. If you pass a handler for an Identity that is already registered
  // the previous handler will be silently overwriten.