code: public static boolean isEditingModelGroups(CmsObject cms, CmsResource containerPage) {
  
          return (OpenCms.getResourceManager().getResourceType(containerPage).getTypeName().equals(
              CmsResourceTypeXmlContainerPage.MODEL_GROUP_TYPE_NAME)
              && OpenCms.getRoleManager().hasRole(cms, CmsRole.DEVELOPER));
      }
docs: Checks whether the current page is a model group page.<p>
  
  @param cms the CMS context
  @param containerPage the current page
  
  @return <code>true</code> if the current page is a model group page