AvlNode<E> newTop = pred();
        // newTop is the maximum node in my left subtree
        newTop.left = left.removeMax(newTop);
        newTop.right = right;
        newTop.distinctElements = distinctElements - 1;
        newTop.totalCount = totalCount - oldElemCount;
        return newTop.rebalance();
      } else {
        AvlNode<E> newTop = succ();

        AvlNode<E> newTop = pred();
        // newTop is the maximum node in my left subtree
        newTop.left = left.removeMax(newTop);
        newTop.right = right;
        newTop.distinctElements = distinctElements - 1;
        newTop.totalCount = totalCount - oldElemCount;
        return newTop.rebalance();
      } else {
        AvlNode<E> newTop = succ();

        validateApi(body, messages -> {});
        final EditBody newBody = new EditBody();
        AdminGeneralAction.updateForm(fessConfig, newBody);
        BeanUtil.copyBeanToBean(body, newBody, CopyOptions::excludeNull);
        AdminGeneralAction.updateConfig(fessConfig, newBody);
        return asJson(new ApiResponse().status(Status.OK).result());
    }