docs: public String getRdfaAttr() {
  
          String result = "";
          CmsObject cms = obtainCmsObject();
          if (cms != null) {
              if (isDirectEditEnabled(cms)) {
                  if (m_contentValue != null) {
                      // within the offline project return the OpenCms specific entity id's and property names
                      result = CmsContentService.getRdfaAttributes(m_contentValue);
                  } else if ((m_nullValueInfo != null)) {
                      if (m_nullValueInfo.getParentValue() != null) {
                          result = CmsContentService.getRdfaAttributes(
                              m_nullValueInfo.getParentValue(),
                              m_nullValueInfo.getValueName());
                      } else if (m_nullValueInfo.getContent() != null) {
                          result = CmsContentService.getRdfaAttributes(
                              m_nullValueInfo.getContent(),
                              m_nullValueInfo.getLocale(),
                              m_nullValueInfo.getValueName());
                      }
                  }
              } else {
                  // TODO: return mapped property names etc. when online
              }
          }
          return result;
      }