code: Set<CmsUUID> getOpenItemIds() {
  
          Set<CmsUUID> result = new HashSet<CmsUUID>();
          for (CmsLazyTreeItem item : m_items) {
              CmsSitemapEntryBean entryBean = item.getData();
              if (item.isOpen()) {
                  result.add(entryBean.getStructureId());
              }
          }
          return result;
      }
docs: Collects the structure ids belonging to open tree entries.<p>
  
  @return the collected set of structure ids