DrilldownEvent is not firing in multi-level drill down chart

Flow
1

I have multi-level drill down chart. I have added drilldown callback as below:
chart.setDrilldownCallback(new DrilldownCallback() {
@Override
public Series handleDrilldown(DrilldownEvent event) {
System.out.println("inside DrilldownEvent ");
return event.getSeries();
}
});
Unfortunately the event not fired.So I tried addPointClickListener. But as per the link https://github.com/vaadin/charts/issues/448 , I am not able to get any useful information from PointClickListener.
How to get leaf level clicked item in multi-level drill-down chart? Can anyone help on this?
Thanks !!!