code: public static boolean isLegalPropertyKey(String key)
    {
  
      return (key.equals(OutputKeys.CDATA_SECTION_ELEMENTS)
              || key.equals(OutputKeys.DOCTYPE_PUBLIC)
              || key.equals(OutputKeys.DOCTYPE_SYSTEM)
              || key.equals(OutputKeys.ENCODING)
              || key.equals(OutputKeys.INDENT)
              || key.equals(OutputKeys.MEDIA_TYPE)
              || key.equals(OutputKeys.METHOD)
              || key.equals(OutputKeys.OMIT_XML_DECLARATION)
              || key.equals(OutputKeys.STANDALONE)
              || key.equals(OutputKeys.VERSION)
              || (key.length() > 0) 
                    && (key.charAt(0) == '{') 
                    && (key.lastIndexOf('{') == 0)
                    && (key.indexOf('}') > 0)
                    && (key.lastIndexOf('}') == key.indexOf('}')));
    }
docs: Report if the key given as an argument is a legal xsl:output key.
  
  @param key non-null reference to key name.
  
  @return true if key is legal.