import React from "react";
export declare function notEmpty<TValue>(value: TValue | null | undefined): value is TValue;
export type RequireOnlyOne<T, Keys extends keyof T = keyof T> = Pick<T, Exclude<keyof T, Keys>> & {
    [K in Keys]-?: Required<Pick<T, K>> & Partial<Record<Exclude<Keys, K>, undefined>>;
}[Keys];
export declare const isBrowser: () => boolean;
export declare const useFocus: () => [React.RefObject<HTMLInputElement>, () => void];