code: func indexDelete(storer Storer, tx *bolt.Tx, key []byte, originalData interface{}) error {
  	indexes := storer.Indexes()
  
  	for name, index := range indexes {
  		err := indexUpdate(storer.Type(), name, index, tx, key, originalData, true)
  		if err != nil {
  			return err
  		}
  	}
  
  	return nil
  }
docs: // removes an item from the index
  // be sure to pass the data from the old record, not the new one