Django unique slug

models.py

from django.db import models
from django.urls import reverse
from unidecode import unidecode #pip install unidecode
from django.utils.crypto import get_random_string
from django.utils.text import slugify

from taggit.managers import TaggableManager

class Blog(models.Model):
    title = models.CharField(max_length=256)
    slug = models.SlugField(max_length=256, unique=True)
    body = models.TextField(null=True, blank=True)
    created = models.DateTimeField()
    publish = models.BooleanField(default=False)
    image = models.ImageField(upload_to='uploads/', null=True, blank=True)
    tags = TaggableManager()

    def get_absolute_url(self):
        return reverse('blog-detail', kwargs={'slug': self.slug})

    def _uniquify(self):
        slug = slugify(unidecode(self.title))
        num = len(Blog.objects.filter(slug=slug))
        unique_slug = '{}-{}'.format(slug, num+1) if num > 0 else slug
        return unique_slug

    def save(self, *args, **kwargs):
        self.slug = self._uniquify()
        super(Blog, self).save(*args, **kwargs)
        
    def __str__(self):
        return self.title