code: private AsyncCallback shutdownASG() {
      Optional<List<String>> optionalLaunchConfigurationNames = Optional
          .of(Arrays.asList(this.masterLaunchConfigName, this.workerLaunchConfigName));
      Optional<List<String>> optionalAutoScalingGroupNames = Optional
          .of(Arrays.asList(this.masterAutoScalingGroupName, this.workerAutoScalingGroupName));
  
      return new AWSShutdownHandler(this.awsSdkClient,
          optionalLaunchConfigurationNames,
          optionalAutoScalingGroupNames);
    }
docs: *
  Callback method that deletes {@link AutoScalingGroup}s
  @return Callback method that deletes {@link AutoScalingGroup}s