JS - how to use newer version of dhtmlxgantt.js file

Hello,

I am using this Javascript file in our application, https://api.knack.com/v1/applications/[application_id]/download/asset/5a014db0089ef6514b929b6f/dhtmlxgantt.js, whose version is this: dhtmlxGantt v.4.2.1 Professional.

Using this, basic Gantt chart functionality is working fine.

But now, I want to implement Group By feature on Column(s) of Gantt Chart, which is not working with this version of javascript file, and getting this error: gantt.groupBy is not a function.

Can someone please help, how to use newer version of dhtmlxgantt.js file to solve this issue ?

Thanks in advance.