protected function populate_question_numbers() {
        $number = 1;
        foreach ($this->slots as $slot) {
            if ($this->questions[$slot->questionid]->length == 0) {
                $slot->displayednumber = get_string('infoshort', 'quiz');
            } else {
                $slot->displayednumber = $number;
                $number += 1;
            }
        }
    }