What's wrong, I can't understand Manager?

Question

SQLite

I do everything according to the points as shown, and during the launch of the web application it gives me such an error, I can’t understand what the problem is?

from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import Column, Integer, String, DateTime
from flask_migrate import Migrate, MigrateCommand, Manager
from datetime import datetime
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import LoginManager, UserMixin, login_required
from flask_mail import Mail, Message

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///usersinfo.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config['MAIL_USERNAME'] = '[email protected]'
app.config['MAIL_DEFAULT_SENDER'] = '[email protected]'
app.config['MAIL_PASSWORD'] = 'password'
manager = Manager(app)
manager.add_command('db', MigrateCommand)
db = SQLAlchemy(app)
migrate = Migrate(app, db)
mail = Mail(app)
login_manager = LoginManager(app)
login_manager.login_view = 'login'


@login_manager.user_loader
def load_user(user_id):
    return db.session.query(Users).get(user_id)


class Users(db.Model, UserMixin):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    username = Column(String(80), unique=True, nullable=False)
    email = Column(String(100), unique=True, nullable=False)
    password_hash = Column(String(80), nullable=False)
    created_on = Column(DateTime(), default=datetime.utcnow)
    updated_on = Column(DateTime(), default=datetime.utcnow, onupdate=datetime.utcnow)

    def __repr__(self):
        return "<{}:{}>".format(self.id, self.username)

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password_hash, password)


db.create_all()

db.session.commit()


@app.route('/admin/')
@login_required
def admin():
    return render_template('admin.html')


app.run(port=5001)

-------------------------------------------------- -----
Error: C:\Users\user8\PycharmProjects\web>python start.py
Traceback (most recent call last):
File "start.py", line 19, in
manager = Manager(app)
TypeError: ' NoneType' object is not callable

Answer 1

draw the 19th line with the code, what's there