export declare class AssociateBy<T> {
    /**
     * Returns a map consisting of the elements mapped by the given `keySelector`.
     *
     * @param {(value: T) => Promise<K> | K} keySelector
     * @returns {Promise<Map<K, T>>}
     */
    associateBy<K>(keySelector: (value: T) => Promise<K> | K): Promise<Map<K, T>>;
    /**
     * Returns a map consisting of the elements indexed by the given `key`.
     *
     * @param {K} key
     * @returns {Map<T[K], T>}
     */
    associateBy<K extends keyof NonNullable<T>>(key: K): Promise<Map<NonNullable<T>[K], T>>;
    /**
     * Returns a map consisting of the elements mapped by the given `keySelector`. The value
     * is transformed into another value by the `valueTransformer`.
     *
     * @param {(value: T) => Promise<K> | K} keySelector
     * @param {(value: T) => Promise<V> | V} valueTransformer
     * @returns {Map<K, V>}
     */
    associateBy<K, V>(keySelector: (value: T) => Promise<K> | K, valueTransformer: (value: T) => Promise<V> | V): Promise<Map<K, V>>;
    /**
     * Returns a map consisting of the elements indexed by the given `key`. The value
     * is transformed into another value by the `valueTransformer`.
     *
     * @param {K} key
     * @param {(value: T) => Promise<V> | V} valueTransformer
     * @returns {Map<K, V>}
     */
    associateBy<K extends keyof NonNullable<T>, V>(key: K, valueTransformer: (value: T) => Promise<V> | V): Promise<Map<NonNullable<T>[K], V>>;
}