Flex AdvancedDataGrid identify selected item is folder.brach or leaf

Flex:

itemclick="itemClick(event)"

Code:
private var _currentGroupLabel:String;
private var _isSelectedContentFolder:Boolean=true;
private function itemClick(event:ListEvent):void
{
var obj:* = event.itemRenderer.data;

//If the selected item has children, it is a folder/branch
_isSelectedContentFolder = (obj.hasOwnProperty("children") && obj.children!=null) ? true : false;

//Cache a reference of the folder/branch label
_currentGroupLabel = _isSelectedContentFolder ? obj.GroupLabel : "";

//Alert.show(_currentGroupLabel+" "+_isSelectedContentFolder.toString());
if(!_isSelectedContentFolder)
{
onClickTree();
}
}