if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(namespaceURI)) return Collections.singleton(XMLConstants.XMLNS_ATTRIBUTE).iterator();
  public Iterator getPrefixes(String namespaceURI)  {    if (XMLConstants.XML_NS_URI.equals(namespaceURI))      return Collections.singleton(XMLConstants.XML_NS_PREFIX).iterator();    LinkedList acc = new LinkedList();    for (Iterator i = namespaces.iterator(); i.hasNext(); )      {        LinkedHashMap ctx = (LinkedHashMap) i.next();        if (ctx.containsValue(namespaceURI))          {            for (Iterator j = ctx.entrySet().iterator(); j.hasNext(); )              {                Map.Entry entry = (Map.Entry) i.next();                String uri = (String) entry.getValue();                if (uri.equals(namespaceURI))                  acc.add(entry.getKey());              }          }      }    return acc.iterator();  }