export declare function average(source: Iterable<number | PromiseLike<number>> | AsyncIterable<number>, selector?: (x: number) => number | Promise<number>): Promise<number>;
export declare function average<TSource>(source: Iterable<TSource | PromiseLike<TSource>> | AsyncIterable<TSource>, selector?: (x: TSource) => number | Promise<number>): Promise<number>;