def _activate_top( self, event ) :
        """internal routine to reset focus to menu button which
        opens sub-menu. Used when an arrow key is used in a sub-menu
        to return to the parent menu"""

        w = event.widget
        if self._parent is not None and self._parent._current_widget :
            w.configure( state = NORMAL )
            w = self._parent._current_widget
            w.configure( state =  ACTIVE )
            w.focus_set()
internal routine to reset focus to menu button which
        opens sub-menu. Used when an arrow key is used in a sub-menu
        to return to the parent menu
recipes/Python/442500_ExtraMenu__TkInter_menu_arbitrary_widgets/recipe-442500.py