code: func GetNddPrefixForRegion(regionCode string, stripNonDigits bool) string {
  	var metadata *PhoneMetadata = getMetadataForRegion(regionCode)
  	if metadata == nil {
  		return ""
  	}
  	var nationalPrefix string = metadata.GetNationalPrefix()
  	// If no national prefix was found, we return an empty string.
  	if len(nationalPrefix) == 0 {
  		return ""
  	}
  	if stripNonDigits {
  		// Note: if any other non-numeric symbols are ever used in
  		// national prefixes, these would have to be removed here as well.
  		nationalPrefix = strings.Replace(nationalPrefix, "~", "", -1)
  	}
  	return nationalPrefix
  }
docs: // Returns the national dialling prefix for a specific region. For example,
  // this would be 1 for the United States, and 0 for New Zealand. Set
  // stripNonDigits to true to strip symbols like "~" (which indicates a
  // wait for a dialling tone) from the prefix returned. If no national prefix
  // is present, we return null.
  //
  // Warning: Do not use this method for do-your-own formatting - for some
  // regions, the national dialling prefix is used only for certain types
  // of numbers. Use the library's formatting functions to prefix the
  // national prefix when required.