Google Play Rresponses Developer API Error

Hi I am using Google Play Developer API to validate subscription purchase on my own server. Here is the official procurement documentation. Subscriptions: get method:

https://developers.google.com/android-publisher/api-ref/purchases/subscriptions/get#response

The problem is that the documentation only shows the result if it succeeds. There is no error list. How should I handle them on my server if I don't know the answers?