Filter assignment group to specific groups that current assigned_to user is a member of

Hello, all.

I recently setup an advanced reference qualifier on our assignment_group field to return groups that the assigned_to user is a member of. I'd like to further filter that query to show only a specific group type of "itil" and hoping one of you cold assist. Below is the script we're using...

javascript: 'sys_idIN' + new global.ArrayUtil().convertArray(gs.getUser().getUserByID(current.assigned_to.toString()).getMyGroups())