django admin带mptt子级的嵌套内联线

我想知道是否有可能创建一个具有多个嵌套内联线的ModelAdmin,如:

1. 合同
   • 主要产品
     • 子管道1
     • 子管道2
       • 子产品

我还试图用mptt解决模型。 我的模型如下所示:

class Contract(models.Model):    
    contractnumber =  models.CharField(max_length=25)
    field2 =  models.CharField(max_length=25)
    field3 =  models.CharField(max_length=25)
    field4 =  models.CharField(max_length=25)

    def __str__(self):
        return self.field1

    class Meta:
        verbose_name = 'Contract'
        verbose_name_plural = 'Contracts'

class Mainproduct(MPTTModel):
    pr_c_contractnumber = models.ForeignKey(Contract)
    pr_name = models.Charfield(max_length=50)
    productdetails = models.Textfield(max_length=5000)
    pr_sernr = models.CharField(max_length=50)
    parent = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True,
                            on_delete=models.SET_NULL)

    def __str__(self):
        return self.pr_c_contractnumber, self.pr_name

    class MPTTMeta:
        order_insertation_by = ['pr_sernr']

    class Meta:
        verbose_name = 'Product'
        verbose_name_plural = 'Products'

我的管理员。py文件如下所示:

class ProductModelInlineForm(forms.ModelForm):
    parent = TreeNodeChoiceField(queryset=Product.objects.all())

class ProductModelInline(admin.TabularInline):
    model = Product
    form = ProductModelInlineForm
    extra = 1

class ProductAdmin(admin.ModelAdmin):
    inlines = [ProductModelInline, ]

class ProductInline(admin.TabularInline):
    model = Product
    extra = 1

class ContractAdmin(admin.ModelAdmin):
    inlines = [ProductInline, ]

有没有办法创建这些嵌套的内联线?我错过了什么重要的事情吗?