Doctrine\ODM\MongoDB\Configuration::getMetadataDriverImpl PHP Method

    public function getMetadataDriverImpl()
    {
        return isset($this->attributes['metadataDriverImpl']) ?
            $this->attributes['metadataDriverImpl'] : null;
    }

 /**
  * Set the association mappings of a metadata.
  *
  * @param ClassMetadataInfo $metadata
  * @param Configuration     $configuration
  */
 protected function setAssociationMappings(ClassMetadataInfo $metadata, Configuration $configuration)
 {
     $supportedClasses = $configuration->getMetadataDriverImpl()->getAllClassNames();
     foreach (class_parents($metadata->getName()) as $parent) {
         if (in_array($parent, $supportedClasses)) {
             $parentMetadata = new MongoClassMetadata($parent);
             $configuration->getMetadataDriverImpl()->loadMetadataForClass($parent, $parentMetadata);
             foreach ($parentMetadata->associationMappings as $key => $value) {
                 if ($this->hasRelation($value['association'])) {
                     $metadata->associationMappings[$key] = $value;
                 }
             }
         }
     }
 }