Google App Engine KeyProperty无法使用它

Question

我实际上是在python中编写Web服务代码，而我无法将值存储到KeyProperty值中。我有一对多的关系（Item - ＆gt; Category）。我想将我的类别ID存储在Item类的category字段中。这是我的代码：

class Item(ndb.Model):
    name = ndb.StringProperty(required=True, indexed=True)
    desc = ndb.StringProperty(required=True)
    price = ndb.FloatProperty(required=True)
    category = ndb.KeyProperty(kind='Categorie', repeated=True)

class Category(ndb.Model):
    name = ndb.StringProperty(required=True, indexed=True)

class ItemHandler（webapp2.RequestHandler）：

def insert(self, item_ID):
    try:
        keyItem = ndb.Key('Item', item_ID)
        item = keyItem.get()

        if item is None:
            status = 201
            item = Item(key=keyItem)
        else:
            status = 200

        dict = json.loads(self.request.body)

        keyCategory = ndb.Key('Category', dict['category'])
        cat = ndb.Key('Categorie', item_dict_in['categorie']).get()

        # If data doesn't exist, I insert it
        if cat is None:

            cat.name = dict['categorie']
            me.put();
# continue, all work fine after to write the output.

有人可以帮助我吗？

Tancks