/**
 * converts undefined or a scalar into an array, leaves existing array
 * untouched
 *
 * useful for cleansing input when you want to allow user to optionally
 * provide a singular scalar for convenience, e.g.:
 * cache.findById(53) and cache.findById([53. 78, 99])
 */
export declare function toArray(val: null | undefined): [];
export declare function toArray<T, U>(val: T | [T] | [T, U]): [T] | [T, U];
export declare function toArray<T>(val: T | T[] | undefined | null): T[];