docs: @SuppressWarnings("unchecked")
      private static Map<String, Boolean> getRenderedStylesheetResources(FacesContext facesContext)
      {
          Map<String, Boolean> map = (Map<String, Boolean>) facesContext.getAttributes().get(
                  RENDERED_STYLESHEET_RESOURCES_SET);
          if (map == null)
          {
              map = new HashMap<String, Boolean>();
              facesContext.getAttributes().put(RENDERED_STYLESHEET_RESOURCES_SET,map);
          }
          return map;
      }