func (s *openshiftImageSource) GetSignatures(ctx context.Context, instanceDigest *digest.Digest) ([][]byte, error) {
	var imageName string
	if instanceDigest == nil {
		if err := s.ensureImageIsResolved(ctx); err != nil {
			return nil, err
		}
		imageName = s.imageStreamImageName
	} else {
		imageName = instanceDigest.String()
	}
	image, err := s.client.getImage(ctx, imageName)
	if err != nil {
		return nil, err
	}
	var sigs [][]byte
	for _, sig := range image.Signatures {
		if sig.Type == imageSignatureTypeAtomic {
			sigs = append(sigs, sig.Content)
		}
	}
	return sigs, nil
}
func (s *openshiftImageSource) GetSignatures(ctx context.Context, instanceDigest *digest.Digest) ([][]byte, error) {
	var imageName string
	if instanceDigest == nil {
		if err := s.ensureImageIsResolved(ctx); err != nil {
			return nil, err
		}
		imageName = s.imageStreamImageName
	} else {
		imageName = instanceDigest.String()
	}
	image, err := s.client.getImage(ctx, imageName)
	if err != nil {
		return nil, err
	}
	var sigs [][]byte
	for _, sig := range image.Signatures {
		if sig.Type == imageSignatureTypeAtomic {
			sigs = append(sigs, sig.Content)
		}
	}
	return sigs, nil
}
// GetSignatures returns the image's signatures.  It may use a remote (= slow) service.
// If instanceDigest is not nil, it contains a digest of the specific manifest instance to retrieve signatures for
// (when the primary manifest is a manifest list); this never happens if the primary manifest is not a manifest list
// (e.g. if the source never returns manifest lists).