public function getDocumentPersister($documentName)
{
if (!isset($this->persisters[$documentName])) {
$class = $this->dm->getClassMetadata($documentName);
$pb = $this->getPersistenceBuilder();
$this->persisters[$documentName] = new Persisters\DocumentPersister($pb, $this->dm, $this->evm, $this, $this->hydratorFactory, $class);
}
return $this->persisters[$documentName];
}