code: func Parse(pair string) (k, v string) {
  	parts := strings.SplitN(pair, ":", 2)
  	k = parts[0]
  	if len(parts) > 1 {
  		v = parts[1]
  	} else {
  		// this pair is invalid. This should not happen in practice.
  		// Do not panic because this function is used for externally-supplied
  		// data.
  	}
  	return
  }
docs: // Parse parses a colon-delimited key-value pair.
  //
  // If pair does not have ":", the whole string becomes the key with an empty
  // value.