code: public static DesignContextMenu getInstance() {
          Page page = ExecutionContext.getPage();
          DesignContextMenu contextMenu = page.getAttribute(DesignConstants.ATTR_DESIGN_MENU, DesignContextMenu.class);
  
          if (contextMenu == null) {
              contextMenu = create();
              page.setAttribute(DesignConstants.ATTR_DESIGN_MENU, contextMenu);
          }
  
          return contextMenu;
      }
docs: Returns an instance of the design context menu. This is a singleton with the page scope and
  is cached once created.
  
  @return The design context menu for the active page.