Any sample code or docs for modifying AST nodes?

[wabbadabbadub]

Hello,

I've been searching all over this repo with no result for a way to modify AST nodes using AstRewriter. I cannot find any sample snippet to begin with.
I've tried modifying the values on each node, but they're readonly (I guess due to performance reasons).
I'd be grateful if you could provide some beginners guide related to that, because I'm kinda lost.
Sorry for opening this as an issue, I couldn't find another way.

Thanks.