apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/controller/ItemController.java/ItemController/createYaml
class ItemController:    @Override
    protected Yaml createYaml() {
      LoaderOptions loaderOptions = new LoaderOptions();
      loaderOptions.setAllowDuplicateKeys(false);
      return new Yaml(new SafeConstructor(), new Representer(),
          new DumperOptions(), loaderOptions);
    }