import { IterableX } from '../iterable';
/**
 * Flattens the source sequence until the specified depth.
 * @param {Iterable<T>} source Source sequence.
 * @param {Number} depth The depth to flatten the source sequence.
 * @returns {Iterable<T>} The flattened sequence, flattened to the specified depth.
 */
export declare function flatten<T>(source: Iterable<T>, depth?: number): IterableX<T>;