/**
 * Returns all distinct elements that appear in any of the given arrays
 *
 * Example:
 *
 * ```ts
 * import { union } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
 * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
 *
 * const soupIngredients = [ 'Pepper', 'Carrots', 'Leek' ]
 * const saladIngredients = [ 'Carrots', 'Radicchio', 'Pepper' ]
 * const shoppingList = union(soupIngredients, saladIngredients)
 *
 * assertEquals(shoppingList, [ 'Pepper', 'Carrots', 'Leek', 'Radicchio' ])
 * ```
 */
export declare function union<T>(...arrays: (readonly T[])[]): T[];