How to create a unique_for_field slug in Django?

Question

Django has a unique_for_date property you can set when adding a SlugField to your model. This causes the slug to be unique only for the Date of the field you specify:

Answer 1

What about unique_together?

class Example(models.Model):
    title = models.CharField()
    slug = models.SlugField(db_index=False)
    category = models.ForeignKey(Category)

    class Meta:
        unique_together = (('slug','category'),)
        # or also working since Django 1.0:
        # unique_together = ('slug','category',)

This creates an index, but it is not outside of Django ;) Or did I miss the point?