/**
 * Custom hook that returns a function indicating whether the component
 * is mounted or not.
 *
 * @returns A function that returns a boolean value indicating whether
 *          the component is mounted.
 *
 * @example
 * const isMounted = useIsMounted();
 * console.log(isMounted()); // true
 *
 */
export declare function useIsMounted(): () => boolean;