code: func TruncateID(id string) string {
  	if i := strings.IndexRune(id, ':'); i >= 0 {
  		id = id[i+1:]
  	}
  	if len(id) > shortLen {
  		id = id[:shortLen]
  	}
  	return id
  }
docs: // TruncateID returns a shorthand version of a string identifier for convenience.
  // A collision with other shorthands is very unlikely, but possible.
  // In case of a collision a lookup with TruncIndex.Get() will fail, and the caller
  // will need to use a longer prefix, or the full-length Id.