code: func (o *RolloutHistoryOptions) Validate() error {
  	if len(o.Resources) == 0 && cmdutil.IsFilenameSliceEmpty(o.Filenames, o.Kustomize) {
  		return fmt.Errorf("required resource not specified")
  	}
  	if o.Revision < 0 {
  		return fmt.Errorf("revision must be a positive integer: %v", o.Revision)
  	}
  
  	return nil
  }
docs: // Validate makes sure all the provided values for command-line options are valid