Hi zzz,

Checked in odoo about this, First of all we have two JS structures in Odoo 16.

For OWL: odoo.define we have example 

self. displayNotification({ title: result. warning, type: 'danger' }); GOLD

this. displayNotification({ title: result. warning, type: 'danger' });

For OWL: /* @odoo-module */ we have example 

this.widget.displayNotification({

message: this.env._t("No available collaborator, please

try again later."),

sticky: true,

}); 

Use 'This' and 'Self' According to functionality of function.

Hope this answer will help you.

Thanks & Regards,
Email:  odoo@aktivsoftware.com
Skype: kalpeshmaheshwari