Doctrine\MongoDB\Aggregation\Stage\Out::out PHP Method

    public function out($collection)
    {
        $this->collection = (string) $collection;
        return $this;
    }

 /**
  * @param ClassMetadata $classMetadata
  * @return $this
  *
  * @throws MappingException
  */
 private function fromDocument(ClassMetadata $classMetadata)
 {
     if ($classMetadata->isSharded()) {
         throw MappingException::cannotUseShardedCollectionInOutStage($classMetadata->name);
     }
     return parent::out($classMetadata->getCollection());
 }