code: protected Set<String> getElementIds() {
  
          Set<String> subItems = new HashSet<String>();
          Iterator<Widget> it = m_groupContainer.iterator();
          while (it.hasNext()) {
              Widget w = it.next();
              if (w instanceof CmsContainerPageElementPanel) {
                  subItems.add(((CmsContainerPageElementPanel)w).getId());
              }
          }
          subItems.add(m_groupContainer.getId());
          return subItems;
      }
docs: Returns the ids of the contained elements and group-container itself.<p>
  
  @return the element ids