async getItem(itemPosition) {
        const items = await $(this.rootElement).$$('li[data-id="sidebar-item-li"]');
        if (items[itemPosition]) {
            return new PageSidebarItem(
                `${this.rootElement} li[data-id="sidebar-item-li"]:nth-child(${itemPosition + 1})`,
            );
        }
        return null;
    }
Return a new SidebarItem page object of the element in item position.
@method
@param {number} itemPosition - The base 0 index of the sidebar item