How to make a group in JavaScript

I want to grouping some shapes in JavaScript.
I tried to search on web, but I couldn’t find that.

First, I will select some shapes, but I couldn’t find how to select.
I found ‘assemble’ method, this method to make group.

Please, tell me how to select some shapes, and grouping shapese.

I solved this issue.

It is bug for OmniGraffle.
I tried to use ‘hackRef’ method written on the page, I solved it !!

In particular,

// ‘shapes’ are array of shape(graffle.Shape object).
graffle.assemble(hackRef(, shapes)