How to use the puput.models.Category function in puput

if parent.parent and parent.parent == self:
                raise ValidationError(_('Cannot have circular Parents.'))

    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.name)
        return super(Category, self).save(*args, **kwargs)

    class Meta:
        ordering = ['name']
        verbose_name = _("Category")
        verbose_name_plural = _("Categories")


class CategoryEntryPage(models.Model):
    category = models.ForeignKey(Category, related_name="+", verbose_name=_('Category'), on_delete=models.CASCADE)
    page = ParentalKey('EntryPage', related_name='entry_categories')
    panels = [
        FieldPanel('category')
    ]

    def __str__(self):
        return str(self.category)


class TagEntryPage(TaggedItemBase):
    content_object = ParentalKey('EntryPage', related_name='entry_tags')


@register_snippet
class Tag(TaggitTag):
    objects = TagManager()

def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.name)
        return super(Category, self).save(*args, **kwargs)