Doctrine\ODM\MongoDB\DocumentManager::persist PHP Method

    public function persist($document)
    {
        if (!is_object($document)) {
            throw new \InvalidArgumentException(gettype($document));
        }
        $this->errorIfClosed();
        $this->unitOfWork->persist($document);
    }

 public function updateAttendee(AttendeeInterface $attendee)
 {
     $attendee->setUpdatedAt(new \DateTime());
     $this->em->persist($attendee);
     $this->em->flush();
     return true;
 }