public void insert(User entity) {
        doInsert(entity, null);
    }

    public void insert(User entity, RequestOptionCall<IndexRequestBuilder> opLambda) {
        entity.asDocMeta().indexOption(opLambda);
        doInsert(entity, null);
    }

    public void update(User entity) {
        doUpdate(entity, null);
    }

  private final IteratorOperation newAddMethod() {
    Object toInsert = elementsToInsert.next();
    return new IteratorOperation() {
      @Override
      public @Nullable Object execute(Iterator<?> iterator) {
        @SuppressWarnings("unchecked")
        ListIterator<Object> rawIterator = (ListIterator<Object>) iterator;
        rawIterator.add(toInsert);
        return null;
      }
    };
  }

  private final IteratorOperation newAddMethod() {
    Object toInsert = elementsToInsert.next();
    return new IteratorOperation() {
      @Override
      public @Nullable Object execute(Iterator<?> iterator) {
        @SuppressWarnings("unchecked")
        ListIterator<Object> rawIterator = (ListIterator<Object>) iterator;
        rawIterator.add(toInsert);
        return null;
      }
    };
  }