private static function get_assignments_course_structure() {
        return new external_single_structure(
            array(
                'id' => new external_value(PARAM_INT, 'course id'),
                'fullname' => new external_value(PARAM_TEXT, 'course full name'),
                'shortname' => new external_value(PARAM_TEXT, 'course short name'),
                'timemodified' => new external_value(PARAM_INT, 'last time modified'),
                'assignments' => new external_multiple_structure(self::get_assignments_assignment_structure(), 'assignment info')
              ), 'course information object'
        );
    }