constructor(nodes, similarities, size) {
		this.nodes = nodes;
		this.similarities = similarities;
		this.size = size || sumSize(nodes);
		/** @type {string | undefined} */
		this.key = undefined;
	}
@param {Node<T>[]} nodes nodes
@param {number[] | null} similarities similarities between the nodes (length = nodes.length - 1)
@param {Record<string, number>=} size size of the group