import { LinkedList } from "./LinkedList";
export declare class ListNode<T> {
    prev: ListNode<T>;
    next: ListNode<T>;
    list: LinkedList<T>;
    value: T;
    constructor(_value: T);
    append(value: T): ListNode<T>;
    toString(): string;
}
export declare class NullNode extends ListNode<any> {
    constructor();
}
export declare const NULL_NODE: NullNode;