Python '；SQLALCHEMY_数据库_URI'；运行Flask应用程序时不在app.config中出错

尝试运行Flask应用程序时，我遇到以下与sqlalchemy相关的错误：

'SQLALCHEMY_DATABASE_URI' not in app.config and
AttributeError: module 'auth_.server' has no attribute 'config'

Flask应用程序的我的目录结构：

parent dir
- index.py
 auth_
  - server.py

server.py的内容

from flask import Flask

server = Flask(__name__,instance_relative_config=False)

server.config['SECRET_KEY'] = 'xxxxxxxxx'
server.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///db.sqlite'
server.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False