Where did the Parse.Collection.extend method go in the Parse.com SDK?

Question

JavaScript

Greetings,
please tell me where the Parse.Collection.extend method has gone from the Parse.com SDK and what has come to replace it? The link from Google to the SDK https://parse.com/docs/js/api/classes/Parse.Collec... gives a 404 error. When accessing the Parse.Collection.extend method from the application, it swears:

Uncaught TypeError: Cannot read property 'extend' of undefined

How to be then?