如何实现把node拖拽到Group中的功能

看DemoUtils#initNetworkDragAndDropListener方法，里面有一段查找当前鼠标下是否有Group的代码。
然后把LinkEditorDemo#onDragDrop类似改一把
代码:
            var group:Group = null;
            if(element is Node && dragImage){
               Node(element).centerLocation = centerLocation;  
               var list:ICollection = network.getElementsByDisplayObject(dragImage);
               for(var i:int=0; i<list.count; i++){
                  group = list.getItemAt(i) as Group;
                  if(group != null){
                     break;
                  }
               }
            }
            if(group != null){
               element.parent = group;
            }