由于未加载模型，因此无法创建表单字段

Question

这是我的模特

class AbstractSubnet(TimeStampedEditableModel):
    subnet = NetworkField(default="10.0.0.0/24")
    description = models.CharField(max_length=100, blank=True)
    master_subnet = models.ForeignKey('self', on_delete=models.CASCADE,
                                      blank=True, null=True,
                                      related_name="child_subnets")

    class Meta:
        abstract = True

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

形式：

class AbstractSubnetAdminForm(forms.ModelForm):

    class Meta:
        model = AbstractSubnet
        fields = '__all__'

这给了我以下错误，我想这也很明显，

ValueError: Cannot create form field for 'master_subnet' yet, because its related model 'django_ipam.Subnet' has not been loaded yet

解决这个问题的方法是什么？