public static function get_annotations($gradeid, $pageno, $draft) {
        global $DB;

        $params = array('gradeid'=>$gradeid, 'pageno'=>$pageno, 'draft'=>1);
        if (!$draft) {
            $params['draft'] = 0;
        }
        $annotations = array();
        $records = $DB->get_records('assignfeedback_editpdf_annot', $params);
        foreach ($records as $record) {
            array_push($annotations, new annotation($record));
        }

        return $annotations;
    }