docs: protected void initPreview(Element root, CmsXmlContentDefinition contentDefinition) throws CmsXmlException {
  
          String preview = root.attributeValue(APPINFO_ATTR_URI);
          if (preview == null) {
              throw new CmsXmlException(
                  Messages.get().container(
                      Messages.ERR_XMLCONTENT_MISSING_PREVIEW_URI_2,
                      root.getName(),
                      contentDefinition.getSchemaLocation()));
          }
          m_previewLocation = preview;
      }