public function load(Identifier $identifier, $document = null, $lockMode = LockMode::NONE)
    {
        $qb     = $this->dm->createQueryBuilder($this->class->name);
        $query  = $qb->get()->setIdentifier($identifier)->getQuery();
        $result = $query->getSingleMarshalledResult();

        return $result ? $this->createDocument($result, $document) : null;
    }