/**
 * Converts an integer to a Roman numeral string.
 *
 * @param {number} num The number to convert to a Roman numeral.
 * @returns {string} The Roman numeral string.
 *
 * @example
 * toRomanNumeral(4) // "IV"
 * toRomanNumeral(9) // "IX"
 * toRomanNumeral(2023) // "MMXXIII"
 */
export declare function toRomanNumeral(num: number): string;