防止ndb数据存储区中的重复属性

from google.appengine.ext import ndb

class MyModel(ndb.Model):
    unique_property = ndb.StringProperty(unique=True)

@ndb.transactional
def store_data():
    # 检查属性是否已存在
    if MyModel.query(MyModel.unique_property == 'value').get():
        return

    # 创建新实体并存储
    entity = MyModel(unique_property='value')
    entity.put()

def check_duplicate_property(value):
    query = MyModel.query(MyModel.unique_property == value)
    return query.get() is not None