There is a MAXScript command to figure out whether an object is part of a group:
But I needed to know which group it was in. And there is no
whichGroupAmIIn <node> function...
There is no need for the function because groups are basically a form of hierarchy, so you can just use
<node>.parent to find the parent.
To check you have the group you can check the class and superclass:
Classof should return Dummy and
superclassof should return helper.