Doctrine\ODM\MongoDB\UnitOfWork::fixPersistentCollectionOwnership PHP Method

    private function fixPersistentCollectionOwnership(PersistentCollectionInterface $coll, $document, ClassMetadata $class, $propName)
    {
        $owner = $coll->getOwner();
        if ($owner === null) {
            // cloned
            $coll->setOwner($document, $class->fieldMappings[$propName]);
        } elseif ($owner !== $document) {
            // no clone, we have to fix
            if (!$coll->isInitialized()) {
                $coll->initialize();
                // we have to do this otherwise the cols share state
            }
            $newValue = clone $coll;
            $newValue->setOwner($document, $class->fieldMappings[$propName]);
            $class->reflFields[$propName]->setValue($document, $newValue);
            if ($this->isScheduledForUpdate($document)) {
                // @todo following line should be superfluous once collections are stored in change sets
                $this->setOriginalDocumentProperty(spl_object_hash($document), $propName, $newValue);
            }
            return $newValue;
        }
        return $coll;
    }