public static function get_bulk($ids, $returnfields = 'id, name, rawname, tagcollid') {
        global $DB;
        $result = array();
        if (empty($ids)) {
            return $result;
        }
        list($sql, $params) = $DB->get_in_or_equal($ids);
        $records = $DB->get_records_select('tag', 'id '.$sql, $params, '', $returnfields);
        foreach ($records as $record) {
            $result[$record->id] = new static($record);
        }
        return $result;
    }