Rhythm - Workset.Create Not Working

Hi Guys,

I was trying to find a way of creating workset through Dynamo and found few custom nodes for making worksets. Tried all of them and return in “Null” . I’m not sure what I’m doing wrong and read an old post here : http://dynamobim.org/forums/topic/rhythm-workset-create/. Based on that my system should work with this node.
I’m running revit 2015 R3.

Can anyone suggest solution for this ?

Cheers