code: func (sm SignedManifest) References() []distribution.Descriptor {
  	dependencies := make([]distribution.Descriptor, len(sm.FSLayers))
  	for i, fsLayer := range sm.FSLayers {
  		dependencies[i] = distribution.Descriptor{
  			MediaType: "application/vnd.docker.container.image.rootfs.diff+x-gtar",
  			Digest:    fsLayer.BlobSum,
  		}
  	}
  
  	return dependencies
  
  }
docs: // References returns the descriptors of this manifests references