One-off operation to be queued and executed in isolate pool
Whatever fields are dedfined in the instance will be passed to isolate.
The generic type
E determines the return type of the job.
Be considerate of Dart's rule defining what types can cross isolate bounaries, i.e. you will
have challenges with objects that wrap native resources (e.g. fil handles).
You may reffer to Dart's SendPort.send for details on the limitations.