func UnparsedInstance(src types.ImageSource, instanceDigest *digest.Digest) *UnparsedImage {
	return &UnparsedImage{
		src:            src,
		instanceDigest: instanceDigest,
	}
}
func UnparsedInstance(src types.ImageSource, instanceDigest *digest.Digest) *UnparsedImage {
	return &UnparsedImage{
		src:            src,
		instanceDigest: instanceDigest,
	}
}
// UnparsedInstance returns a types.UnparsedImage implementation for (source, instanceDigest).
// If instanceDigest is not nil, it contains a digest of the specific manifest instance to retrieve (when the primary manifest is a manifest list).
//
// The UnparsedImage must not be used after the underlying ImageSource is Close()d.