addChoices(values, labels) {
		const sb = this.node;
		const ul = sb.querySelector('ul');
		const lis = ul ? ul.querySelectorAll('li[data-value]') : [];

		if (!Array.isArray(values))
			values = L.toArray(values);

		if (!L.isObject(labels))
			labels = {};

		for (let i = 0; i < values.length; i++) {
			let found = false;

			for (let j = 0; j < lis.length; j++) {
				if (lis[j].getAttribute('data-value') === values[i]) {
					found = true;
					break;
				}
			}

			if (found)
				continue;

			ul.insertBefore(
				this.createChoiceElement(sb, values[i], labels[values[i]]),
				ul.lastElementChild);
		}
	}
Add new choices to the dropdown menu.

This function adds further choices to an existing dropdown menu,
ignoring choice values which are already present.

@instance
@memberof LuCI.ui.Dropdown
@param {string[]} values
The choice values to add to the dropdown widget.

@param {Object<string, *>} labels
The choice label values to use when adding dropdown choices. If no
label is found for a particular choice value, the value itself is used
as label text. Choice labels may be any valid value accepted by
{@link LuCI.dom#content}.