code: func (precondition *ScalePrecondition) ValidateJob(job *extensions.Job) error {
  	if precondition.Size != -1 && job.Spec.Parallelism == nil {
  		return PreconditionError{"parallelism", strconv.Itoa(precondition.Size), "nil"}
  	}
  	if precondition.Size != -1 && *job.Spec.Parallelism != precondition.Size {
  		return PreconditionError{"parallelism", strconv.Itoa(precondition.Size), strconv.Itoa(*job.Spec.Parallelism)}
  	}
  	if len(precondition.ResourceVersion) != 0 && job.ResourceVersion != precondition.ResourceVersion {
  		return PreconditionError{"resource version", precondition.ResourceVersion, job.ResourceVersion}
  	}
  	return nil
  }
docs: // ValidateJob ensures that the preconditions match.  Returns nil if they are valid, an error otherwise.