ToplevelList system = cdlDocument.getSystem();
SystemElement system = cdlDocument.getSystem();
    public void testElementExtension1() throws Exception {        ParseContext context = new ParseContext();        CdlDocument cdlDocument = parseValidCDL(context,                CDL_DOC_EXTENDS_1);        //xpath tests to verify the stuff        ToplevelList system = cdlDocument.getSystem();        PropertyList a3 = system.getChildTemplateMatching("", "a3");    }