code: public static E164PhoneNumberWithExtension ofPhoneNumberStringAndExtension(String phoneNumber, String extension, CountryCode defaultCountryCode) {
      	return new E164PhoneNumberWithExtension(phoneNumber, extension, defaultCountryCode);
      }
docs: Creates a new E164 Phone Number with the given extension.
  @param phoneNumber The phone number in arbitrary parseable format (may be a national format)
  @param extension The extension, or null for no extension
  @param defaultCountryCode The Country to apply if no country is indicated by the phone number
  @return A new instance of E164PhoneNumberWithExtension