code: protected int _parent(int identity)
    {
  
      if (identity < m_size)
        return m_parent.elementAt(identity);
  
      // Check to see if the information requested has been processed, and,
      // if not, advance the iterator until we the information has been
      // processed.
      while (true)
      {
        boolean isMore = nextNode();
  
        if (identity >= m_size && !isMore)
          return NULL;
        else if (identity < m_size)
          return m_parent.elementAt(identity);
      }
    }
docs: Get the parent for the given node identity.
  
  @param identity The node identity.
  
  @return The parent identity, or DTM.NULL.