I use Sequelize and in my User model have a hook and a prototype (see below). On the second line of the hook, I try to reference the prototype. But this doesn't work. It returns

this.getAllUsersInclMembersis not a function

How can I call upon the prototype from inside the hook?

module.exports = (sequelize) => {

    User.afterUpdate(async (options) => {
        // here I try to call upon the prototype for the instance
        let users = await this.getAllUsersInclMembers();
        await Promise.all(
            await users.forEach(async (user) => {
                // here we reference to a prototype in another model
                user.syncToDb();
            })
        );
    });

    User.prototype.getAllUsersInclMembers = function {
        return sequelize.models.Product.findAll({
            where: { user_id: this.getDataValue("id") },
        });
    };

};

Update: I've updated the hook to the code below but still with the same result:

User.afterUpdate(async function (user, options) {
    // here I try to call upon the prototype for the instance
    let users = await this.getAllUsersInclMembers();
    await Promise.all(
        await users.forEach(async (user) => {
            // here we reference to a prototype in another model
            user.syncToDb();
        })
    );
});