How to place Layersets into Layersets.

I have checked the forum and I found how to place a layer into a layerset but when I try to apply the same method for placing a layerset into a layerset I get this error.

Illegal Argument. .....

This is the code that I am using:

    var OccLivery_01Lay = app.activeDocument.layerSets.add(); 

    var OccLivery_02Lay = app.activeDocument.layerSets.add();

    var OccMkLay = app.activeDocument.layerSets.add();

    //renaming Layers

    OccGroupLay.name = ('OCC');

    OccLivery_01Lay.name = ('Livery_01');

    OccLivery_02Lay.name = ('Livery_02');

    OccMkLay.name = ('MK');   

   OccLivery_01Lay.move(OccGroupLay, ElementPlacement.INSIDE);