code: public void warn(XPathContext xctxt, String msg, Object args[])
            throws javax.xml.transform.TransformerException
    {
  
      String formattedMsg = XSLMessages.createWarning(msg, args);
      ErrorListener errHandler = xctxt.getErrorListener();
  
      errHandler.warning(new TransformerException(formattedMsg,
                                               (SAXSourceLocator)xctxt.getSAXLocator()));
    }
docs: Warn the user of a problem.
  
  @param xctxt The XPath runtime state.
  @param msg Warning message key
  @param args Arguments to be used in warning message
  @throws XSLProcessorException thrown if the active ProblemListener and XPathContext decide
  the error condition is severe enough to halt processing.
  
  @throws javax.xml.transform.TransformerException