code: public Observable<RefreshIndex> refreshIndexMethodAsync(String listId, String language) {
          return refreshIndexMethodWithServiceResponseAsync(listId, language).map(new Func1<ServiceResponse<RefreshIndex>, RefreshIndex>() {
              @Override
              public RefreshIndex call(ServiceResponse<RefreshIndex> response) {
                  return response.body();
              }
          });
      }
docs: Refreshes the index of the list with list Id equal to list ID passed.
  
  @param listId List Id of the image list.
  @param language Language of the terms.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the RefreshIndex object