protected static function get_chart($labels, $data) {
        $chart = new \core\chart_bar();
        $chart->set_labels($labels);
        $chart->get_xaxis(0, true)->set_label(get_string('grade'));

        $yaxis = $chart->get_yaxis(0, true);
        $yaxis->set_label(get_string('participants'));
        $yaxis->set_stepsize(max(1, round(max($data) / 10)));

        $series = new \core\chart_series(get_string('participants'), $data);
        $chart->add_series($series);
        return $chart;
    }