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* [NEW] PriorityPool for prioritized get/put requests
* [NEW] Queue.when_at_most() and when_at_least() events (18)
* [NEW] Pool.when_at_most() and when_at_least() events (18)
* [CHANGE] Remove Queue.when_new() event
* [CHANGE] Gas station example uses Pool/Pool.when_at_most() (18)
* [FIX] Add API docs for desmod.pool