code: func NewIndex(path, name string) (*Index, error) {
  	err := validateName(name)
  	if err != nil {
  		return nil, errors.Wrap(err, "validating name")
  	}
  
  	return &Index{
  		path:   path,
  		name:   name,
  		fields: make(map[string]*Field),
  
  		newAttrStore: newNopAttrStore,
  		columnAttrs:  nopStore,
  
  		broadcaster:    NopBroadcaster,
  		Stats:          stats.NopStatsClient,
  		logger:         logger.NopLogger,
  		trackExistence: true,
  	}, nil
  }
docs: // NewIndex returns a new instance of Index.