docs: public List<CmsContainerPageElementPanel> getAllDragElements() {
  
          List<CmsContainerPageElementPanel> elements = new ArrayList<CmsContainerPageElementPanel>();
          Iterator<Widget> it = iterator();
          while (it.hasNext()) {
              Widget w = it.next();
              if (w instanceof CmsContainerPageElementPanel) {
                  elements.add((CmsContainerPageElementPanel)w);
              } else {
                  if (CmsDomUtil.hasClass(
                      org.opencms.ade.containerpage.client.ui.css.I_CmsLayoutBundle.INSTANCE.containerpageCss().groupcontainerPlaceholder(),
                      w.getElement())) {
                      CmsDebugLog.getInstance().printLine("Ignoring group container placeholder.");
                  } else {
                      CmsDebugLog.getInstance().printLine(
                          "WARNING: " + w.toString() + " is no instance of CmsDragContainerElement");
                  }
              }
          }
          return elements;
      }