Entering a Subvariation

[migoeu]

I am a total beginner, thus sorry for asking:

Let's say I have a pgn with comments and subvariations, for example starting like this:

1. e4 e5 { Open Game } 2. Nf3 { The main move. } ( 2. d4 { Center Game } ....

I managed to print out all the comments for the mainline with the following code:

for node in game.mainline():
print(node.comment)

I tried several things but I simply don't manage to get a specific comment of the mainline or even more important one of a specific subline.
I wonder how I can print out the comment of the second move "The main move" only?
And what would I need to write to get the comment of the subvariatn with 2.d4: "Center Game" ?
I tried it for several hours, I found something with "node.variations" or "GameNode" in the internet which might be the right thing to use. Unfortunately I failed to implement any of this.
Thank you for any suggestion or idea.