How to create separate file to generate different table of database Flask-SqlAlchemy?

I using Flask-Restplus and SqlAlchemy to create my table and Api.The problem I facing is like below:

At first I have this user.py which having 2 table inside:

User.py

class User(db.Model):
    __tablename__ = "users_info"

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.Integer, unique=True, nullable=True)
    device = db.relationship('Device', backref='user')
    # .. some other field here


class Device(db.Model):
    __tablename__ = "user_device"

    device_id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    id = db.Column(db.Integer, db.ForeignKey(User.id))
    # .. some other field here

At this point,I using this 2 command below with manage.py to create the database,and have no problem.

python manage.py db migrate

python manage.py db upgrade

manage.py

import os
import unittest

from flask_migrate import Migrate, MigrateCommand
from flask_script import Manager
from app import blueprint

from app.main import create_app, db

app = create_app(os.getenv('My_App') or 'dev')
app.register_blueprint(blueprint)

app.app_context().push()

manager = Manager(app)

migrate = Migrate(app, db)

manager.add_command('db', MigrateCommand)


@manager.command
def run():
    app.run()


if __name__ == '__main__':
    manager.run()

Now I want to create another file called product.py,which is a new table for the same database like below:

Product.py

from .. import db
from .model.user import User


class Product(db.Model):
    __tablename__ = "product"

    product_id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    product_name = db.Column(db.String)
    # plan here what you want in this table
    user_id = db.Column(db.Integer, db.ForeignKey(User.user_id))

As you can see Product class is having relationship with User with the foreignKey.

Result:

But I use the same command above to migrate again,the result is look like this :

INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.env] No changes in schema detected.

It seems like didn't detect the new table from my new file.

My Question:

How to create separate file to generate different table of database?