class type['a]int64_serializer_t =object..end
method serialized : int64 ->
(Unixqueue.event_system -> 'a Uq_engines.engine) -> 'a Uq_engines.enginelet se = serialized i f: If already a serializer is running for
the passed value of i, it is waited until the previous engines reach
a final state, and then it is run e = f esys.
se enters a final state when e does.
method multi_serialized : int64 list ->
(Unixqueue.event_system -> 'a Uq_engines.engine) -> 'a Uq_engines.enginelet se = serialized il f: Same as serializing over all values of
il (in a nested way)