将（related_name）分配给继承的ForeignKey字段是否可行（a）和（b）优良作法-Django2.0

Question

我已尝试通过PublisherPolicyManager使用BasePolicy中“进程” ForeignKey的“ policies” related_name进行反向查询。产生错误：

AttributeError: 'RelatedManager' object has no attribute 'valid'

是否有一种方法，PublishedPolicy类可以为'process'字段分配一个不同的related_name，以允许Process反向查询指向PublishedPolicy而不是BasePolicy？

还是逻辑完全有缺陷？

class BasePolicy(models.Model):
    title = models.CharField(max_length = 100)
    process = models.ForeignKey(Process, null=True, blank=True, on_delete=models.SET_NULL, related_name='policies')
    force_read_again = models.BooleanField(default=False)


class DraftPolicy(BasePolicy):
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def publish(self):
        PublishedPolicy.objects.create(
                                 draft_policy = self,
                                 title=self.title,
                                 policy=self.policy,
                                 force_read_again=self.force_read_again)
                                 process=self.process)


class PublishedPolicyManager(models.Manager):

    def current(self):
        return super().get_queryset().exclude(archived_at__isnull=True)

    def valid(self):
        print('here')
        return super().get_queryset().exclude(force_read_again=True, archived_at__isnull=False)


class PublishedPolicy(BasePolicy):
    objects = PublishedPolicyManager()
    draft_policy = models.ForeignKey(DraftPolicy, on_delete=models.SET_NULL, null=True)
    published_at = models.DateTimeField(auto_now_add=True)
    archived_at = models.DateTimeField(null=True)


class PolicyReadManager(models.Manager):
    def valid(self):
        return super().filter(policy__in=PublishedPolicy.objects.valid())


class PolicyRead(models.Model):
    objects = PolicyReadManager()
    policy = models.ForeignKey(PublishedPolicy, on_delete=models.CASCADE)
    user =  models.ForeignKey(User, on_delete=models.CASCADE, related_name='policies_read')
    read_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return '{user} read {policy} at {read_at}'.format(user=user, policy=policy, read_at=read_at)


class Process(models.Model):
    name = models.CharField(max_length=50)
    description = models.TextField()


class ProcessAllocation(models.Model):
    process = models.ForeignKey(Process, on_delete=models.CASCADE)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    allocated_at = models.DateTimeField(auto_now=True, editable=False)

    def policies_outstanding(self):
        policies = self.process.policies(manager='objects').valid()
        read = self.user.policies_read(manager='objects').valid()
        return policies.exclude(id__in=read)