groupbylazy: Use client < self.bot which is a stricter comparison
groupbylazy: Use client < self.bot which is a stricter comparison

client < self.bot or client < self.bufbot makes no difference in the
no-buffering case, except that with `bot` the compiler has to track one
more used field. `bot` is better in the buffering case, we don't have to
visit .lookup_buffer() as often.

imp/rust-itertools,flo-l/rust-itertools,rust-itertools/itertools,tempbottle/rust-itertools