Show the discount code field on checkout for specified levels, hide on others

my_pmpro_show_hide_discount_code.php

<?php
/**
 * Show the discount code field on checkout for specific levels only
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 * 
 */
function my_pmpro_show_hide_discount_code() {
	global $pmpro_show_discount_code;

	if ( ! $pmpro_show_discount_code || ! function_exists( 'pmpro_getLevelAtCheckout' ) || ! function_exists( 'pmpro_is_checkout' ) ) {
		return;
	}

	if ( pmpro_is_checkout() ) {
		$level = pmpro_getLevelAtCheckout();

		if ( ! empty( $level ) ) {
			$level_id = $level->id;

			if ( ! in_array( $level_id , array( 2, 3 ) ) ) { // show discount code field for level 2 and 3 only
				$pmpro_show_discount_code = false;
			}
		}
	}
}
add_action( 'wp', 'my_pmpro_show_hide_discount_code' );