Before the eventing model, the way to find deliveries with changed status was in a per-connection work list.
pn_work_head() for the first.
pn_work_next() to traverse the list.
In the eventing model, this information is available to applications via the PN_DELIVERY callback in Proton C. In the python binding there are specific callbacks: on_message(), on_accepted(), on_rejected(), on_released(), and on_settled().
Mark the use of this older work queue as deprecated to allow removal in a future release.