code: func ResolveCacheImporterFunc(sm *session.Manager) remotecache.ResolveCacheImporterFunc {
  	return func(ctx context.Context, attrs map[string]string) (remotecache.Importer, specs.Descriptor, error) {
  		dgstStr := attrs[attrDigest]
  		if dgstStr == "" {
  			return nil, specs.Descriptor{}, errors.New("local cache importer requires explicit digest")
  		}
  		dgst := digest.Digest(dgstStr)
  		store := attrs[attrSrc]
  		if store == "" {
  			return nil, specs.Descriptor{}, errors.New("local cache importer requires src")
  		}
  		csID := contentStoreIDPrefix + store
  		cs, err := getContentStore(ctx, sm, csID)
  		if err != nil {
  			return nil, specs.Descriptor{}, err
  		}
  		info, err := cs.Info(ctx, dgst)
  		if err != nil {
  			return nil, specs.Descriptor{}, err
  		}
  		desc := specs.Descriptor{
  			// MediaType is typically MediaTypeDockerSchema2ManifestList,
  			// but we leave it empty until we get correct support for local index.json
  			Digest: dgst,
  			Size:   info.Size,
  		}
  		return remotecache.NewImporter(cs), desc, nil
  	}
  }
docs: // ResolveCacheImporterFunc for "local" cache importer.