/**
 * Base class to quickly provide parent-child relationships.
 * @typeParam TNode - Your sub-class.
 */
export declare abstract class TreeNode<TNode> {
    #private;
    /**
     * The parent.
     * @returns The parent.
     */
    get parent(): TNode | undefined;
    /**
     * The children.
     * @returns The children.
     */
    get children(): Set<TNode>;
    /**
     * Construct tree node.
     * @param parent - The parent.
     */
    constructor(parent?: TNode);
    /**
     * Register a new child on the tree.
     * @param child - A new child.
     * @returns The child.
     */
    child(child: TNode): TNode;
}