code: func partition(s, sep string) (string, string) {
  	if strings.Contains(s, sep) {
  		parts := strings.SplitN(s, sep, 2)
  		return parts[0], parts[1]
  	} else {
  		return s, ""
  	}
  }
docs: // Split the string at the first occurrence of sep, and return the part before the separator,
  // and the part after the separator.
  //
  // If the separator is not found, return the string itself, followed by an empty string.