code: func (scaler *JobScaler) ScaleSimple(namespace, name string, preconditions *ScalePrecondition, newSize uint) error {
  	job, err := scaler.c.Jobs(namespace).Get(name)
  	if err != nil {
  		return ScaleError{ScaleGetFailure, "Unknown", err}
  	}
  	if preconditions != nil {
  		if err := preconditions.ValidateJob(job); err != nil {
  			return err
  		}
  	}
  	parallelism := int(newSize)
  	job.Spec.Parallelism = &parallelism
  	if _, err := scaler.c.Jobs(namespace).Update(job); err != nil {
  		if errors.IsInvalid(err) {
  			return ScaleError{ScaleUpdateInvalidFailure, job.ResourceVersion, err}
  		}
  		return ScaleError{ScaleUpdateFailure, job.ResourceVersion, err}
  	}
  	return nil
  }
docs: // ScaleSimple is responsible for updating job's parallelism.