how to create association instance from source instance with sequelize

Question

I have 1:n association User -> Cart, what I want is, I find User by Id then create Cart by that instance and then fill the product_id manually

I'm using sequelize

I have tried get,set,create from this association and none of them worked, it gave me this error

TypeError: user.createCart is not a function
    at /home/horus/beginner-html-site-scripted/server/controllers/Cart.controller.ts:21:26

and this is my CartController:

const { product_id } = req.params;
    const product = await ProductModel.findByPk(product_id);
    if (!product) {
        return res.status(401).json({ message: 'product not found' });
    }
    //@ts-ignore
    const userData = req.user;
    const user = await UserModel.findByPk(userData.user_id);
    if (!user) return res.status(401).json({ message: 'user not found' });
    const cart = await user.createCart();

    res.status(200).json({ message: '', cartData: user.getCart() });

those are my Models:

Cart Class

export default class Cart
    extends Model<InferAttributes<Cart>, InferCreationAttributes<Cart>>
    implements CartInterface {
    declare cart_id: CreationOptional<string>;
    declare quantity: CreationOptional<number>;
    declare user_id: string;
}
Cart.init(
    {
        cart_id: { type: UUID, defaultValue: UUIDV4, primaryKey: true },
        quantity: { type: INTEGER, defaultValue: 1 },
        user_id: {
            type: UUID,
            references: {
                model: 'Users',
                key: 'user_id',
            },
        },
    },
    { sequelize: db, tableName: 'Carts' }
);

User Class

export default class User
    extends Model<InferAttributes<User>, InferCreationAttributes<User>>
    implements UserInterface {
    declare user_id: CreationOptional<string>;
    declare firstName: string;
    declare lastName: string;
    declare email: string;
    declare password: string;
    declare avatar: string;
    declare verificationCode: CreationOptional<string>;
    declare passwordResetCode: CreationOptional<string>;
    declare verified: CreationOptional<boolean>;
    declare isAdmin: CreationOptional<boolean>;
    // timestamps!
    // createdAt can be undefined during creation
    declare createdAt: CreationOptional<Date>;
    // updatedAt can be undefined during creation
    declare updatedAt: CreationOptional<Date>;

    declare createSession: HasManyCreateAssociationMixin<Session, 'user_id'>;
    declare createCart: HasOneCreateAssociationMixin<CartModel>;
    declare setCart: HasOneSetAssociationMixin<CartModel, 'cart_id'>;
    declare getCart: HasOneGetAssociationMixin<CartModel>;
}
User.init(
    {
        user_id: {
            primaryKey: true,
            allowNull: false,
            type: UUID,
            defaultValue: UUIDV4,
        },
        firstName: { type: new STRING(128), allowNull: false },
        lastName: { type: new STRING(128), allowNull: false },
        email: { type: new STRING(128), allowNull: false, unique: true },
        password: {
            type: new STRING(128),
            allowNull: false,
        },
        avatar: { type: new STRING(128), defaultValue: '' },
        verificationCode: { type: UUID, allowNull: false, defaultValue: UUIDV4 },
        passwordResetCode: { type: UUID, allowNull: false, defaultValue: '' },
        verified: { type: BOOLEAN, defaultValue: false, allowNull: false },
        isAdmin: { type: BOOLEAN, defaultValue: false, allowNull: false },
        createdAt: DATE,
        updatedAt: DATE,
    },
    {
        sequelize: db,
        tableName: 'Users',
    }
);

user Data

User {
  dataValues: {
    user_id: '20b42b70-f777-420b-b15b-cbf3732c1a9b',
    firstName: 'leo',
    lastName: 'qal',
    email: '[email protected]',
    password: '$2.',
    avatar: '',
    verificationCode: '',
    passwordResetCode: '',
    verified: true,
    isAdmin: true,
    createdAt: 2022-02-17T16:49:40.000Z,
    updatedAt: 2022-02-17T16:49:40.000Z
  },
  _previousDataValues: {
    user_id: '20b42b70-f777-420b-b15b-cbf3732c1a9b',
    firstName: 'leo',
    lastName: 'qal',
    email: '[email protected]',
    password: '$2.',
    avatar: '',
    verificationCode: '',
    passwordResetCode: '',
    verified: true,
    isAdmin: true,
    createdAt: 2022-02-17T16:49:40.000Z,
    updatedAt: 2022-02-17T16:49:40.000Z
  },
  uniqno: 1,
  _changed: Set(0) {},
  _options: {
    isNewRecord: false,
    _schema: null,
    _schemaDelimiter: '',
    raw: true,
    attributes: [
      'user_id',
      'firstName',
      'lastName',
      'email',
      'password',
      'avatar',
      'verificationCode',
      'passwordResetCode',
      'verified',
      'isAdmin',
      'createdAt',
      'updatedAt'
    ]
  },
  isNewRecord: false
}

Associations

UserModel.hasOne(CartModel, {
    sourceKey: 'user_id',
    foreignKey: 'user_id',
    as: 'users',
});
CartModel.belongsTo(UserModel, {
    foreignKey: 'cart_id',
    as: 'carts',
});
//OneToMany Association
UserModel.hasMany(SessionModel, {
    sourceKey: 'user_id',
    foreignKey: 'user_id',
    as: 'sessions', // this determines the name in `associations`!
});

CategoryModel.hasMany(ProductModel, {
    sourceKey: 'category_id',
    foreignKey: 'category_id',
    as: 'products',
});