我刚开始学flask啊，啥也不懂啊，帮我看看啊~

在flask项目中，为了避免循环另外建了个py存放db = SQLAlchemy()，然后在app中引用，然后，问题出现了！

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

from flask import Flask, request, render_template, session, redirect
import config
from flask_migrate import Migrate
from datetime import datetime
from models import SubmissionModel
from middle import db

app = Flask(__name__)
app.config.from_object(config)
db.init_app(app)
migrate = Migrate(app, db)

File "E:\birdfoly.com\flaskProject\models.py", line 7, in

from middle import db

File "E:\birdfoly.com\flaskProject\middle.py", line 8, in
db = SQLAlchemy()
TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

求解救！

发生异常: TypeError
metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
File "E:\birdfoly.com\flaskProject\middle.py", line 8, in
db = SQLAlchemy()
File "E:\birdfoly.com\flaskProject\models.py", line 7, in
from middle import db
File "E:\birdfoly.com\flaskProject\app.py", line 4, in
from models import SubmissionModel

每个人开始的时候都是这，但要坚持！要相信任何事情在付出足够的时间成本之后都会有所收获！熬过这段时间，再回首你会发现不一样的自己

from flask_migrate import Migrate
from fask_script import Manager

manager=Manager(app)
migrate=Migrate(app,db)

尝试在migrate对象上先创建manager对象

有人能解决吗？