code: func getRunningImages() ([]string, error) {
  	var runningImages []string
  	var errors []error
  	err := pkgPod.WalkPods(getDataDir(), pkgPod.IncludeMostDirs, func(p *pkgPod.Pod) {
  		var pm schema.PodManifest
  		if p.State() != pkgPod.Running {
  			return
  		}
  		if !p.PodManifestAvailable() {
  			return
  		}
  		_, manifest, err := p.PodManifest()
  		if err != nil {
  			errors = append(errors, newPodListReadError(p, err))
  			return
  		}
  		pm = *manifest
  		for _, app := range pm.Apps {
  			runningImages = append(runningImages, app.Image.ID.String())
  		}
  	})
  	if err != nil {
  		return nil, err
  	}
  	if len(errors) > 0 {
  		return nil, errors[0]
  	}
  	return runningImages, nil
  }
docs: // getRunningImages will return the image IDs used to create any of the
  // currently running pods