/**
 * Applies the given aggregator to each group in the given Grouping, returning the results together with the respective group keys
 *
 * ```ts
 * import { aggregateGroups } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
 * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
 *
 * const foodProperties = {
 *     'Curry': [ 'spicy', 'vegan' ],
 *     'Omelette': [ 'creamy', 'vegetarian' ],
 * }
 * const descriptions = aggregateGroups(foodProperties,
 *     (current, key, first, acc) => {
 *         if (first)
 *             return `${key} is ${current}`
 *
 *         return `${acc} and ${current}`
 *     },
 * )
 *
 * assertEquals(descriptions, {
 *     'Curry': 'Curry is spicy and vegan',
 *     'Omelette': 'Omelette is creamy and vegetarian',
 * })
 * ```
 */
export declare function aggregateGroups<T, A>(record: Readonly<Record<string, Array<T>>>, aggregator: (current: T, key: string, first: boolean, accumulator?: A) => A): Record<string, A>;