code: @Override
      public PortletRenderResult doRenderMarkup(
              IPortletWindowId portletWindowId,
              HttpServletRequest httpServletRequest,
              HttpServletResponse httpServletResponse,
              PortletOutputHandler portletOutputHandler)
              throws IOException {
  
          // enforce CONFIG mode access restriction through its enforcement in the doRender() impl.
          return doRender(
                  portletWindowId,
                  httpServletRequest,
                  httpServletResponse,
                  portletOutputHandler,
                  RenderPart.MARKUP);
      }
docs: Interacts with the {@link IPortletCacheControlService} to determine if the markup should come
  from cache or not. If cached data doesn't exist or is expired, this delegates to {@link
  #doRender(IPortletWindowId, HttpServletRequest, HttpServletResponse, PortletOutputHandler,
  RenderPart)}.
  
  @throws IOException