code: public static void checkWidgetRequirements(String key, I_CmsFormWidget widget) {
  
          if (widget instanceof CmsTinyMCEWidget) {
              return;
          }
          if (!((widget instanceof I_CmsHasGhostValue) && (widget instanceof HasValueChangeHandlers<?>))) {
              throw new CmsWidgetNotSupportedException(key);
          }
      }
docs: Checks whether a widget can be used in the sitemap entry editor, and throws an exception otherwise.<p>
  
  @param key the widget key
  @param widget the created widget