Detail page error after using slugify in django

I am getting this error when i click on any item detail page. Generic detail view must be called with either an object pk or a slug in the URLconf.

URL:

path('item/<slug:item_slug>/', ItemDetailView.as_view(), name='item_detail'),

VIEW:

class ItemDetailView(DetailView):
    model = Item
    slug_field = 'item_slug'

MODEL:

class Item(models.Model):
    title = models.CharField(max_length=100)
    description= RichTextField(blank=True, null=True)
    main_image= models.ImageField(null=True, blank=True,upload_to='images/')
    date = models.DateTimeField(auto_now_add=True)
    item_category = models.ForeignKey(Categories, default='Coding', on_delete=SET_DEFAULT)
    slug = models.SlugField(unique=True, blank=True, null=True) # new

    

    def save(self, *args, **kwargs):
        if not self.slug and self.title:
            self.slug = slugify(self.title)
        super(Item, self).save(*args, **kwargs)

    def __str__(self):
        return self.title

The URL parameter is specified with the slug_url_kwarg [Django-doc], not the slug_field. The slug_field [Django-doc] is used to filter the queryset, since you use slug for your model, you do not need to change that.

So the view should look like:

class ItemDetailView(DetailView):
    model = Item
    slug_url_kwarg = 'item_slug'