Where can I find the 'youtube-v3-api-captions.json' discovery document?

Question

I'm trying to use the YouTube API to fetch video captions, but the example is incomplete: https://developers.google.com/youtube/v3/code_samples/python#create_and_manage_youtube_video_caption_tracks

Specifically, it has this comment + code:

# Trusted testers can download this discovery document from the developers page
# and it should be in the same directory with the code.
with open("youtube-v3-api-captions.json", "r") as f:
  doc = f.read()
  return build_from_document(doc, http=credentials.authorize(httplib2.Http()))

But it's not at all clear where the youtube-v3-api-captions.json file can be found.

Where can it be found?

Answer 1

It appears to be here: https://www.googleapis.com/discovery/v1/apis/youtube/v3/rest

Which was found by guessing the names "youtube" and "v3" on the Try It section of https://developers.google.com/discovery/v1/reference/apis/getRest