public static synchronized YangXmlUtils getInstance() {
        if (instance == null) {
            instance = new YangXmlUtils();
        }
        return instance;
    }
@Test
    public void testGetXmlUtilsInstance() throws ConfigurationException {

        YangXmlUtils instance1 = YangXmlUtils.getInstance();
        YangXmlUtils instance2 = YangXmlUtils.getInstance();

        assertEquals("Duplicate instance", instance1, instance2);

    }