protected function translateCursor($properties)
    {
        $out = [];
        foreach ($this->sortMap as $k => $v) {
            if (isset($properties[$k])) {
                $d = $v[1] === OrderParameter::DESC ? '!' : '';
                $out[$d . $this->toPublic($k)] = $properties[$k];
            }
        }
        return base64_encode(json_encode($out));
    }