PHP function to add language tag to Welsh posts (to help Mailpoet filter)

add_action('save_post', 'add_langCYTag', 200, 2);
function add_langCYTag ($post_id, $post) {
    $my_current_lang = apply_filters( 'wpml_current_language', NULL);
    if ( $my_current_lang !== 'cy' )
        return;
    $post = get_post( $post_id );
    wp_set_post_tags($post_id, $my_current_lang, true);
}