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

    private function cascadePersist($document, array &$visited)
    {
        $class = $this->dm->getClassMetadata(get_class($document));
        $associationMappings = array_filter($class->associationMappings, function ($assoc) {
            return $assoc['isCascadePersist'];
        });
        foreach ($associationMappings as $fieldName => $mapping) {
            $relatedDocuments = $class->reflFields[$fieldName]->getValue($document);
            if ($relatedDocuments instanceof Collection || is_array($relatedDocuments)) {
                if ($relatedDocuments instanceof PersistentCollectionInterface) {
                    if ($relatedDocuments->getOwner() !== $document) {
                        $relatedDocuments = $this->fixPersistentCollectionOwnership($relatedDocuments, $document, $class, $mapping['fieldName']);
                    }
                    // Unwrap so that foreach() does not initialize
                    $relatedDocuments = $relatedDocuments->unwrap();
                }
                $count = 0;
                foreach ($relatedDocuments as $relatedKey => $relatedDocument) {
                    if (!empty($mapping['embedded'])) {
                        list(, $knownParent, ) = $this->getParentAssociation($relatedDocument);
                        if ($knownParent && $knownParent !== $document) {
                            $relatedDocument = clone $relatedDocument;
                            $relatedDocuments[$relatedKey] = $relatedDocument;
                        }
                        $pathKey = CollectionHelper::isList($mapping['strategy']) ? $count++ : $relatedKey;
                        $this->setParentAssociation($relatedDocument, $mapping, $document, $mapping['fieldName'] . '.' . $pathKey);
                    }
                    $this->doPersist($relatedDocument, $visited);
                }
            } elseif ($relatedDocuments !== null) {
                if (!empty($mapping['embedded'])) {
                    list(, $knownParent, ) = $this->getParentAssociation($relatedDocuments);
                    if ($knownParent && $knownParent !== $document) {
                        $relatedDocuments = clone $relatedDocuments;
                        $class->setFieldValue($document, $mapping['fieldName'], $relatedDocuments);
                    }
                    $this->setParentAssociation($relatedDocuments, $mapping, $document, $mapping['fieldName']);
                }
                $this->doPersist($relatedDocuments, $visited);
            }
        }
    }