code: func (dr *DirReader) StaticSet(ctx context.Context) ([]blob.Ref, error) {
  	if dr.staticSet != nil {
  		return dr.staticSet, nil
  	}
  	staticSetBlobref := dr.ss.Entries
  	if !staticSetBlobref.Valid() {
  		return nil, errors.New("schema/dirreader: Invalid blobref")
  	}
  	members, err := staticSet(ctx, staticSetBlobref, dr.fetcher)
  	if err != nil {
  		return nil, err
  	}
  	dr.staticSet = members
  	return dr.staticSet, nil
  }
docs: // StaticSet returns the whole of the static set members of that directory