code: func (idx *TruncIndex) Get(s string) (string, error) {
  	if s == "" {
  		return "", ErrEmptyPrefix
  	}
  	var (
  		id string
  	)
  	subTreeVisitFunc := func(prefix patricia.Prefix, item patricia.Item) error {
  		if id != "" {
  			// we haven't found the ID if there are two or more IDs
  			id = ""
  			return ErrAmbiguousPrefix{prefix: s}
  		}
  		id = string(prefix)
  		return nil
  	}
  
  	idx.RLock()
  	defer idx.RUnlock()
  	if err := idx.trie.VisitSubtree(patricia.Prefix(s), subTreeVisitFunc); err != nil {
  		return "", err
  	}
  	if id != "" {
  		return id, nil
  	}
  	return "", ErrNotExist
  }
docs: // Get retrieves an ID from the TruncIndex. If there are multiple IDs
  // with the given prefix, an error is thrown.