Undefined type Cocur\Slugify\Slugify

Bonjour,

Voila je rencontre un petit problème avec mon code, je reçois ce message d'erreur : " Undefined type 'Cocur\Slugify\Slugify'. " ?
il ne reconnait pas Slugify: return (new Slugify())->slugify($this->title);

je suis le tutorial Symfony 4 par l'exemple (3/16): découverte de doctrine

Avez vous une idée ?

Ma version Symfony 4.4

Mon source: Property.php

<?php

namespace App\Entity;

use App\Repository\PropertyRepository;
use Doctrine\ORM\Mapping as ORM;
use Cocur\Slugify\Slugify;
............
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..........................................
public function getSlug(): string
    {
        return (new Slugify())->slugify($this->title);
    }

/**
 * @ORM\Entity(repositoryClass=PropertyRepository::class)
 */

Mon source : PropertyController.php :

<?php

namespace App\Controller;

use App\Entity\Property;
use App\Repository\PropertyRepository;
use Doctrine\Common\Persistence\ObjectManager;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;

class PropertyController extends AbstractController
{
    /**
     * @var PropertyRepository
     */
    private $repository;
    /**
     * @var ObjectManager
     */
    private $em;

    public function __construct(PropertyRepository $repository, EntityManagerInterface $em)
    {
        $this->repository = $repository;
        $this->em = $em;
    }

    /**
     * @Route("/biens", name="property.index")
     * @return Response
     */
    public function index(): Response 
    {
        return $this->render('property/index.html.twig', [
            'current_menu' => 'properties'
        ]);
    }

    /**
     * @Route("/biens/{slug}-{id}", name="property.show", requirements={"slug": "[a-z0-9\-]*"})
     * @return Response
     */
    public function show($slug, $id): Response 
    {
        $property = $this->repository->find($id);
        return $this->render('property/show.html.twig', [
            'property' => 'property',
            'current_menu' => 'properties'
        ]);
    }
}