Javascript branch/ CPM.js

I'm trying to call getCurrentBranch that is defined in CPM.js from Captivate:

g.SlideGraphManager.prototype = {
    getCurrentBranch: function () {
        return this.m_CurrentBranch;
    },
}

I guess it's related to this property

(function (g) { g.SlideGraphManager = function () {
this.m_CurrentBranch = []; }; )

I can console log the SlideGraphManager function with cp.SlideGraphManager but no idea how to call getCurrentBranch or access m_CurrentBranch. Any pointers much appreciated!! J