docs: protected void processPageContent(I_PageContentVisitor visitor) {
  
          for (Entry<String, org.opencms.ade.containerpage.client.ui.CmsContainerPageContainer> entry : m_targetContainers.entrySet()) {
  
              CmsContainer cnt = m_containers.get(entry.getKey());
              if (visitor.beginContainer(entry.getKey(), cnt)) {
                  Iterator<Widget> elIt = entry.getValue().iterator();
                  while (elIt.hasNext()) {
                      try {
                          CmsContainerPageElementPanel elementWidget = (CmsContainerPageElementPanel)elIt.next();
                          visitor.handleElement(elementWidget);
                      } catch (ClassCastException e) {
                          // no proper container element, skip it (this should never happen!)
                          CmsDebugLog.getInstance().printLine(
                              "WARNING: there is an inappropriate element within a container");
                      }
                  }
                  visitor.endContainer();
              }
          }
      }