Neos\Flow\Persistence\Doctrine\PersistenceManager::add PHP Method

    public function add($object)
    {
        if (!$this->isNewObject($object)) {
            throw new KnownObjectException('The object of type "' . get_class($object) . '" (identifier: "' . $this->getIdentifierByObject($object) . '") which was passed to EntityManager->add() is not a new object. Check the code which adds this entity to the repository and make sure that only objects are added which were not persisted before. Alternatively use update() for updating existing objects."', 1337934295);
        } else {
            try {
                $this->entityManager->persist($object);
            } catch (\Exception $exception) {
                throw new PersistenceException('Could not add object of type "' . get_class($object) . '"', 1337934455, $exception);
            }
        }
    }