code: func newIndex(root string, indexConf jsonconfig.Obj) (sorted.KeyValue, error) {
  	if len(indexConf) > 0 {
  		return sorted.NewKeyValueMaybeWipe(indexConf)
  	}
  	return sorted.NewKeyValueMaybeWipe(jsonconfig.Obj{
  		"type": defaultIndexType,
  		"file": filepath.Join(root, defaultIndexFile),
  	})
  }
docs: // newIndex returns a new sorted.KeyValue, using either the given config, or the default.