code: func isViablePhoneNumber(number string) bool {
  	if len(number) < MIN_LENGTH_FOR_NSN {
  		return false
  	}
  	return VALID_PHONE_NUMBER_PATTERN.MatchString(number)
  }
docs: // Checks to see if the string of characters could possibly be a phone
  // number at all. At the moment, checks to see that the string begins
  // with at least 2 digits, ignoring any punctuation commonly found in
  // phone numbers. This method does not require the number to be
  // normalized in advance - but does assume that leading non-number symbols
  // have been removed, such as by the method extractPossibleNumber.
  // @VisibleForTesting