protected static function move_policy_document($policyid, $step) {
        global $DB;

        $sortorder = $DB->get_field('tool_policy', 'sortorder', ['id' => $policyid], MUST_EXIST);
        $DB->set_field('tool_policy', 'sortorder', $sortorder + $step, ['id' => $policyid]);
        static::distribute_policy_document_sortorder();
    }