code: private void setupParse ()
    {
      XMLReader p = getParent();
      if (p == null) {
        throw new NullPointerException(XSLMessages.createMessage(XSLTErrorResources.ER_NO_PARENT_FOR_FILTER, null)); //"No parent for filter");
      }
      
      ContentHandler ch = m_transformer.getInputContentHandler();
  //    if(ch instanceof SourceTreeHandler)
  //      ((SourceTreeHandler)ch).setUseMultiThreading(true);
      p.setContentHandler(ch);
      p.setEntityResolver(this);
      p.setDTDHandler(this);
      p.setErrorHandler(this);
    }
docs: Set up before a parse.
  
  <p>Before every parse, check whether the parent is
  non-null, and re-register the filter for all of the
  events.</p>