def _get_selection(self):
        "Returns the index of the selected item (list for multiselect) or None"
        if self.multiselect:
            return self.wx_obj.GetSelections()
        else:
            sel = self.wx_obj.GetSelection()
            if sel == wx.NOT_FOUND:
                return None
            else:
                return sel
Returns the index of the selected item (list for multiselect) or None