code: public void addNodes(NodeIterator iterator)
    {
  
      if (!m_mutable)
        throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESET_NOT_MUTABLE, null)); //"This NodeSet is not mutable!");
  
      if (null != iterator)  // defensive to fix a bug that Sanjiva reported.
      {
        Node obj;
  
        while (null != (obj = iterator.nextNode()))
        {
          addElement(obj);
        }
      }
  
      // checkDups();
    }
docs: Copy NodeList members into this nodelist, adding in
  document order.  Null references are not added.
  
  @param iterator NodeIterator which yields the nodes to be added.
  @throws RuntimeException thrown if this NodeSet is not of
  a mutable type.