gistfile1.py

class Account(PolymorphicMPTTModel):

    parent = PolymorphicTreeForeignKey('self',
                                       null=True,
                                       blank=True,
                                       related_name='children',
                                       verbose_name=_('parent'))
    name = models.CharField(max_length=150, unique=True)
    company_name = models.CharField(max_length=150, unique=True,
                                    help_text=_('Corportate Name'))
    is_active = models.BooleanField(
        _('Active'), default=True,
        help_text="If your account is deactivaded, you can't log in again.")
    unique_identifier = models.CharField(
        max_length=20,
        help_text='Company document number. e.g. SSN')

    def save(self, *args, **kwargs):
        if not self.is_active:
            # cascade updating to deactivate children accounts
            self.get_descendants(True).update(is_active=False)
        super(Account, self).save(*args, **kwargs)



class AccountInfo(models.Model):
    address = models.CharField(max_length=150)
    complement = models.CharField(max_length=150, null=True, blank=True)
    city = models.CharField(max_length=45)
    state = models.CharField(max_length=45)
    postal_code = models.CharField(max_length=15)
    country = models.ForeignKey(Country)

    class Meta:
        abstract = True


class Brand(Account):
    pass


class Company(Account, AccountInfo):
    currency = models.ForeignKey(Currency, null=True, blank=True)


class Reseller(Account, AccountInfo):
    pass


class Client(Account, AccountInfo):
    client_id = models.CharField(max_length=5, null=False, blank=False,
                                 unique=True)