public function unmarshall($object)
    {
        if (isset($object['id'])) {
            $object['$id'] = $object['id'];
            unset($object['id']);
        }

        foreach ($object as $key => $value) {
            if ($key[0] === '_') {
                $key[0] = '$';
                $object[$key] = $value;
            }
        }

        return $object;
    }