GeezerVison

I still have to add a section explaining how the waiting actually happens, using cancellations, and the various cases.

This looks pretty good to my relatively uneducated eye, with just a handful of minor textual/syntax suggestions. A few of the sections got a bit dense at times, but I was able to get the gist of them (despite being a rank beginner) at least after a re-read or two and without much context, and I'm not sure how to explain them more simply.

One high-level thing to consider: Perhaps consider moving the class definition closer to the top of the section, after the introduction/summary line but before the example? I'm not super solid on this, but it feels somewhat out of place at the end (especially with the example being introduced before it), and as a side effect it means that the link from What's New puts the reader at the end of the relevant section rather than the beginning. But I don't feel too strongly about it.

Thank you for taking care of this, Guido. LGTM.