Django SlugField Auto Generate and Unique

from django.db import models
from django.utils.text import slugify


class MyModel(models.Model):
    name = models.CharField()
    slug = models.SlugField(unique=True, null=False)
    def _generate_unique_slug(self)
        unique_slug = slugify(self.name)
        num = 1
        while MyModel.objects.filter(slug=unique_slug).exists():
            slug = '{}-{}'.format(unique_slug, num)
            num += 1
            return unique_slug
    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = self._get_unique_slug()
        super().save(*args, **kwargs)