public static function unpublish($publication) {
        global $DB;
        // Unpublish the publication by web service.
        api::unregister_courses($publication->hubcourseid);

        // Delete the publication from the database.
        $DB->delete_records('course_published', array('id' => $publication->id));

        // Add confirmation message.
        $course = get_course($publication->courseid);
        $context = \context_course::instance($course->id);
        $publication->courseshortname = format_string($course->shortname, true, ['context' => $context]);
        $publication->hubname = 'Moodle.net';
        \core\notification::add(get_string('courseunpublished', 'hub', $publication), \core\output\notification::NOTIFY_SUCCESS);
    }