public static WebServiceClient getWebServiceClient() {
    return instance;
  }
@Test
  void testGetWebServiceClient() throws Exception {
    Configuration conf = new Configuration();
    conf.set(YarnConfiguration.YARN_HTTP_POLICY_KEY, "HTTPS_ONLY");
    WebServiceClient.initialize(conf);
    WebServiceClient client = WebServiceClient.getWebServiceClient();
    assertNotNull(client.getSSLFactory());
    WebServiceClient.destroy();
  }