/**
 * Returns a new callback that will raise an error if called more than once.
 * @param callback The original callback
 * @hidden
 */
export declare function onlyOnce<T>(callback: Callback): Callback;
/**
 * Interface for callback that does not have a result.
 */
export interface Callback {
    (err?: Error): void;
}
/**
 * Generic interface for callback that has a result.
 */
export interface ResultCallback<T> {
    (err?: Error, result?: T): void;
}