addToList = (itemOrItems, list) => {
	if (Array.isArray(itemOrItems)) {
		for (const item of itemOrItems) {
			list.add(item);
		}
	} else if (itemOrItems) {
		list.add(itemOrItems);
	}
}
@template T
@param {T | T[]} itemOrItems item or items
@param {Set<T>} list list