Documentation about `leibnizO`.
Following up on a discussion at Mattermost: https://mattermost.mpi-sws.org/iris/pl/4yeyn4i53bydjbf4g4syfm7q6h
Following up on a discussion at Mattermost: https://mattermost.mpi-sws.org/iris/pl/4yeyn4i53bydjbf4g4syfm7q6h