_getItems() {
		const allItems: Array<IComboBoxItem> = [];

		this._filteredItems.forEach(item => {
			if (isInstanceOfComboBoxItemGroup(item)) {
				const visibleItems = this.open ? item.items.filter(i => i._isVisible) : item.items;
				const groupedItems = [item, ...visibleItems];
				allItems.push(...groupedItems);
				return;
			}

			allItems.push(item);
		});

		return allItems;
	}