I think the idea here is to look at the code for the libraries you're using. The documentation might lead you to believe it behaves in a certain way, but the actual code is the true source of truth. Open it up and have a look instead of wondering.

Something I liked about working at Google is that I never had to wonder what the lifecycle of a certain request looked like. I could always open up the code for the server I was trying to talk to, and piece together what "internal error" really meant, or what "optional" fields were actually required to make the request succeed.