Add line in robots.txt to disallow GPTBot. (WordPress plugin)

disallow-gptbot.php

<?php
/**
 * Plugin Name: Disallow GPTBot
 * Description: Add line in robots.txt to disallow GPTBot.
 * Plugin URI:  https://torstenlandsiedel.de
 * Version:     1.0
 * Author:      Torsten Landsiedel
 * Author URI:  http://torstenlandsiedel.de
 * Licence:     GPL 2
 * License URI: http://opensource.org/licenses/GPL-2.0
 *
 * @package  SEO/Must-Use
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
} // Exit if accessed directly.

/**
 * Add Disallow for GPTBot
 * See: https://platform.openai.com/docs/gptbot
 *
 * @param  string $output The robots.txt output.
 * @return string The modified robots.txt output.
 */
function disallow_gptbot( $output ) {
	$output .= "\nUser-agent: GPTBot\nDisallow: *\n";

	return $output;
}
add_filter( 'robots_txt', 'disallow_gptbot', 10 );