sendJob method
Sends a job to the isolate and returns a Future with the result
Implementation
Future<R> sendJob(T cmd) async {
if (!_isInitialized) {
await initialize();
}
final jobId = _jobId++;
final completer = Completer<R>();
_jobCompleterMap[jobId] = completer;
_isolateSendPort!.send(_Job<T, R>(jobId: jobId, cmd: cmd));
return completer.future;
}