code: func rawInputContainsNationalPrefix(rawInput, nationalPrefix, regionCode string) bool {
  	normalizedNationalNumber := NormalizeDigitsOnly(rawInput)
  	if strings.HasPrefix(normalizedNationalNumber, nationalPrefix) {
  		// Some Japanese numbers (e.g. 00777123) might be mistaken to
  		// contain the national prefix when written without it
  		// (e.g. 0777123) if we just do prefix matching. To tackle that,
  		// we check the validity of the number if the assumed national
  		// prefix is removed (777123 won't be valid in Japan).
  		num, err := Parse(normalizedNationalNumber[len(nationalPrefix):], regionCode)
  		if err != nil {
  			return false
  		}
  		return IsValidNumber(num)
  
  	}
  	return false
  }
docs: // Check if rawInput, which is assumed to be in the national format, has
  // a national prefix. The national prefix is assumed to be in digits-only
  // form.