/**
 * A shim for the `flat()` method that creates a new array with all sub-array
 * elements concatenated into it recursively up to the specified depth
 * @param arr - The array.
 * @param depth - The depth level specifying how deep a nested array
 *                struction should be flattened. Defaults to 1.
 * @returns A new array with the sub-array elements concatenated to it.
 */
export declare function flat(arr: any[], depth?: number): any[];
/**
 * Deduplicates an array's element. Note that order is not preserved.
 * @param arr - The array.
 * @returns A new array containing only unique elements.
 */
export declare function dedupe<T>(arr: T[]): T[];