How do you separate the model using the Flask-SQLAlchemy project structure?

see examples that define the model directly at the start of the program, such as _ _ init__.py, server.py.
my idea is to define the model in the corresponding .py file and create it directly when needed. I don"t know how to organize the project file and call it.
initialization file:

-sharpapp/__init__.py
import os
from flask import Flask

def create_app(test_config=None):
    -sharp create and configure the app
    app = Flask(__name__, instance_relative_config=True)

    if test_config is None:
        -sharp load the instance config, if it exists, when not testing
        app.config.from_pyfile("config.py", silent=True)
    else:
        -sharp load the test config if passed in
        app.config.from_mapping(test_config)

    -sharp instance
    try:
        os.makedirs(app.instance_path)
    except OSError:
        pass

    -sharp
    @app.route("/hello")
    def hello():
        return "Hello, World!"

    -sharp
    from app.models import db
    db.init_app(app)
    print("")
    db.create_all()

    return app

Model file:

-sharpapp/models.py
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()

class Person(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50), nullable=False)
    addresses = db.relationship("Address", backref="person", lazy=True)

class Address(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(120), nullable=False)
    person_id = db.Column(db.Integer, db.ForeignKey("person.id"),
        nullable=False)

it is normal to start the application, but no database tables are generated.

(Flask-Practice) ydx@ydx-PC:$ flask run
 * Serving Flask app "app" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with inotify reloader

 * Debugger is active!
 * Debugger PIN: 338-486-377

Why did you output create Database twice?
an error occurred when accessing the application:

RuntimeError: application not registered on db instance and no application bound to current context

< hr >

refer to Link description the solution is as follows:
modify the initialization file to inform the flask module of the current application using the context.

    -sharp
    from app.models import db
    db.init_app(app)
    with app.app_context():
        print("")
        db.create_all()