public function convertObjectToIdentityArray($object)
    {
        $identifier = $this->getIdentifierByObject($object);
        if ($identifier === null) {
            throw new Exception\UnknownObjectException(sprintf('Tried to convert an object of type "%s" to an identity array, but it is unknown to the Persistence Manager.', get_class($object)), 1302628242);
        }
        return ['__identity' => $identifier];
    }