import { AsyncSequence } from "../../sequency";
export declare class SumBy {
    /**
     * Returns the sum of all numbers specified by the given `selector` function.
     *
     * @param {(value: T) => Promise<number> | number} selector
     * @returns {Promise<number>}
     */
    sumBy<T>(this: AsyncSequence<T>, selector: (value: T) => Promise<number> | number): Promise<number>;
}