Assign level ID 1 after submission of form ID 1

my_gform_after_submission.php

<?php
function my_gform_after_submission( $entry, $form ) {
	if ( ! function_exists( 'pmpro_changeMembershipLevel' ) ) {
		return;
	}
	global $current_user;
	$user_id = $current_user->ID;
	pmpro_changeMembershipLevel( 1, $user_id );
}
add_action( 'gform_after_submission_1', 'my_gform_after_submission', 10, 2);