类型对象“类别”没有属性“ _mptt_meta”

Question

class Category(MPTTModel):
  name = models.CharField(max_length=200, unique=True)
  slug = models.SlugField(max_length=200, unique=True)
  super = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True)

  class MPTTMeta:
  order_insertion_by =['super']

我没有使用MTPP，所以我对这种模型不熟悉。如何显示类别的父类和子类