This is the base class for collections of mouse and digitizer button groups.

Autodesk.AutoCAD.Customization.MenuGroupItemsCollection
    Autodesk.AutoCAD.Customization.ButtonGroupCollection
        Autodesk.AutoCAD.Customization.DigitizerButtonGroupCollection

Public Class ButtonGroupCollection
Inherits MenuGroupItemsCollection

public class ButtonGroupCollection : MenuGroupItemsCollection;