}
  Object getValue(Stylesheet stylesheet, QName mode,                  Node context, int pos, int len)    throws TransformerException  {    if (select != null)      {        return select.evaluate(context, pos, len);      }    else if (children != null)      {        Document doc = (context instanceof Document) ? (Document) context :          context.getOwnerDocument();        DocumentFragment fragment = doc.createDocumentFragment();        children.apply(stylesheet, mode, context, pos, len, fragment, null);        return Collections.singleton(fragment);      }    else      {        return null;      }  }