code: protected void clearTreeLevel(CmsUUID parentId) {
  
          // create a new list to avoid concurrent modifications
          Collection<?> children = m_treeContainer.getChildren(parentId);
          // may be null when monkey clicking
          if (children != null) {
              List<Object> childIds = new ArrayList<Object>(m_treeContainer.getChildren(parentId));
              for (Object childId : childIds) {
                  m_treeContainer.removeItemRecursively(childId);
              }
          }
      }
docs: Clears the given tree level.<p>
  
  @param parentId the parent id