How to make Django slugify not duplicate with Unicode strings?

Question

So basically it works fine, but it creates duplicates of slug for some reason

class News_Tag(models.Model):
    title = models.CharField(max_length=150)
    slug = models.SlugField(null=True, blank=True)

    def __str__(self) -> str:
        return self.title    

    def save(self, *args, **kwargs):
        self.slug = defaultfilters.slugify(unidecode(self.title)) // so with this it creates duplicates
        super().save(*args, **kwargs)

but if i am writting it in that way it works without duplicates but accepting only English words

class News_Tag(models.Model):
    title = models.CharField(max_length=150)
    slug = models.CharField(max_length = 300)

    def __str__(self) -> str:
        return self.title    

    def save(self, *args, **kwargs):
        self.slug = slugify(self.title) // this does not create duplicates but accepting only English words
        super().save(*args, **kwargs)

but I want it to work with different languages and not createing duplicates, is there any ways to do something with first code so that it works without createing duplicates?