code: public BaasResult<Void> logoutSync(String registration) {
          BaasBox box = BaasBox.getDefaultChecked();
          LogoutRequest request = new LogoutRequest(box, this, registration, RequestOptions.DEFAULT, null);
          return box.submitSync(request);
      }
docs: Synchronously logouts current user from the server.
  
  @param registration a registration id to remove
  @return the result of the request