class FilterCategory(models.Model):
    name = models.CharField(_(u'name'), max_length=255)
    slug = AutoSlugField(populate_from='name', unique=True, slugify_function=slugify)


class Filter(models.Model):
    name = models.CharField(_(u'name'), max_length=255)
    slug = AutoSlugField(populate_from='name', unique=True, slugify_function=slugify)
    category = models.ForeignKey(FilterCategory, related_name='filters', verbose_name=_(u'category'))


class Ad(models.Model):
    # Другие поля
    filters = models.ManyToManyField(Filter, verbose_name=_(u'ad filter tags'), blank=True, null=True, related_name="filters")