/**
 * Maps a possibly nullish value to the desired result.
 *
 * Returns `null` if the value is nullish.
 *
 * @param val A value to map.
 * @param cb A function that transforms the value if it is not nullish.
 */
export declare function mapNullable<I, O>(val: I | null | undefined, cb: (val: I) => O): O | null;