export interface RunnableCallback<T> {
    once(...args: any[]): T;
    run(...args: any[]): T;
}
export declare class Callback<T, A extends unknown[]> implements RunnableCallback<T> {
    private readonly callback;
    private isCalled;
    private cache;
    constructor(callback: (...args: A) => T);
    run(...args: A): T;
    once(...args: A): T;
}