export type OneMany<T> = T[] | T;
export type Opt<T> = OneMany<T> | undefined | null;
export declare function toArray<T>(oneMany: OneMany<T>): [T, ...T[]];
export declare function toArray<T>(opt: Opt<T>): T[];
export declare function forEach<T>(opt: Opt<T>, cb: (item: T) => void): void;
export declare function push<T>(opt: Opt<T>, item: T): OneMany<T>;
export declare function push<T>(oneMany: OneMany<T>, item: T): T[];
export declare function concat<T>(opt: Opt<T>, other: Opt<T>): Opt<T>;