Marionette View appendHtml composition not activated

Consider the following composite view of Marionette. Does anyone know the appendHtml event is not firing:

var TreeView = Backbone.Marionette.CompositeView.extend({
template: "#node-template",
tagName: "ul",

initialize: function(){

    this.collection = this.model.nodes;
},

appendHtml: function(collectionView, itemView){

    alert('appendHtml triggered');
    collectionView.$("li:first").append(itemView.el);
}
});

      

        
        
        
      

    

see the warning ('appendHtml triggered'); Why doesn't it work? Has it been removed?