在DJANGO中如何定义get_absolute_url

class Image(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL,
                             related_name='images_created')
    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200, blank=True)
    url = models.URLField()
    image = models.ImageField(upload_to='images/%Y/%m/%d')
    description = models.TextField(blank=True)
    users_like = models.ManyToManyField(settings.AUTH_USER_MODEL,
                                        related_name='images_liked',
                                        blank=True)
    created = models.DateField(auto_now_add=True, db_index=True)

    def get_absolute_url(self):
        return reverse('images:detail', args=[self.id, self.slug])

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

    def __unicode__(self):
        return self.title

ABSOLUTE_URL_OVERRIDES = {
    'auth.user': lambda u: reverse_lazy('user_detail',
                                        args=[u.username])
}