User profiles with inheritance in Django

request.user.get_profile().get_final_profile()

class UpCastModel(models.Model):
    """
    Base class for models that are ment to be inherited.
    Introduces upcast method that returns child instance.
    """
    final_type = models.ForeignKey(ContentType, editable=False)

    def save(self, args, **kwargs):
        if not self.pk:
            self.final_type = ContentType.objects.get_for_model(type(self))
        super(UpCastModel, self).save(args, **kwargs)

    def upcast(self):
        if not hasattr(self, '_upcast'):
            if self.final_type.model_class == self.class:
                self._upcast = self
            else:
                self._upcast = self.final_type.get_object_for_this_type(id=self.pk)
        return self._upcast

    class Meta:
        abstract = True


class UpCastSingleRelatedObjectDescriptor(SingleRelatedObjectDescriptor):

    def get(self, instance, instance_type=None):
        parent = super(
            UpCastSingleRelatedObjectDescriptor, self
        ).get(instance, instance_type)
        return parent.upcast()


class UpCastOneToOneField(models.OneToOneField):
    """
    UpCastOneToOneField gets child of related object.
    """
    def contribute_to_related_class(self, cls, related):
        setattr(
            cls, related.get_accessor_name(),
            UpCastSingleRelatedObjectDescriptor(related)
        )

class BaseProfile(UpcastModel):
    user = UpCastOneToOneField(User)


class BoyProfile(BaseProfile):
    pass


class GirlProfile(CitizenProfile):
    pass