code: func newValidator(image io.ReadSeeker) (*validator, error) {
  	manifest, err := aci.ManifestFromImage(image)
  	if err != nil {
  		return nil, err
  	}
  	v := &validator{
  		image:    image,
  		manifest: manifest,
  	}
  	return v, nil
  }
docs: // newValidator returns a validator instance if passed image is indeed
  // an ACI.