function add_to_map(from, to) {
	from.forEach((exist, element) => {
		to.set(element, higher_existence(exist, to.get(element)));
	});
}
@template T2
@template {T2} T1
@param {Map<T1, NodeExistsValue>} from
@param {Map<T2, NodeExistsValue>} to
@returns {void}