code: func maybeStripInternationalPrefixAndNormalize(
  	number *builder.Builder,
  	possibleIddPrefix string) PhoneNumber_CountryCodeSource {
  
  	numBytes := number.Bytes()
  	if len(numBytes) == 0 {
  		return PhoneNumber_FROM_DEFAULT_COUNTRY
  	}
  	// Check to see if the number begins with one or more plus signs.
  	ind := PLUS_CHARS_PATTERN.FindIndex(numBytes) // Return is an int pair [start,end]
  	if len(ind) > 0 && ind[0] == 0 {              // Strictly match from string start
  		number.ResetWith(numBytes[ind[1]:])
  		// Can now normalize the rest of the number since we've consumed
  		// the "+" sign at the start.
  		number.ResetWithString(normalize(number.String()))
  		return PhoneNumber_FROM_NUMBER_WITH_PLUS_SIGN
  	}
  
  	// Attempt to parse the first digits as an international prefix.
  	iddPattern, ok := readFromRegexCache(possibleIddPrefix)
  	if !ok {
  		pat := possibleIddPrefix
  		iddPattern = regexp.MustCompile(pat)
  		writeToRegexCache(pat, iddPattern)
  	}
  	number.ResetWithString(normalize(string(numBytes)))
  	if parsePrefixAsIdd(iddPattern, number) {
  		return PhoneNumber_FROM_NUMBER_WITH_IDD
  	}
  	return PhoneNumber_FROM_DEFAULT_COUNTRY
  }
docs: // Strips any international prefix (such as +, 00, 011) present in the
  // number provided, normalizes the resulting number, and indicates if
  // an international prefix was present.