anchor.diff:     * Will schedule a [job] after all other queued jobs. If no [Job] is currently
      * waiting, [job] will run.
      */
  -  Future schedule(Job job) {
  +  Future<SparkJobStatus> schedule(Job job) {
       Completer completer = job.completer;
       _waitingJobs.add(job);
   
  
positive.code: import 'package:intl/intl.dart';
  import 'package:logging/logging.dart';
  
  final Logger _logger = new Logger('spark.jobs');
  final NumberFormat _nf = new NumberFormat.decimalPattern();
  
  
negative.code:    * progress monitor. When it finishes, it should complete the [Future] that
     * is returned.
     */
    Future<SparkJobStatus> run(ProgressMonitor monitor);
  
    String toString() => name;
  }
  