anchor.diff:  
   // check if the string contains any surrogate pairs chars
   bool isSurrogatePair(String str) {
  -  return surrogatePairsRegExp.hasMatch(str);
  +  return _surrogatePairsRegExp.hasMatch(str);
   }
   
   
  
positive.code: 
  // check if the string is a hexadecimal number
  bool isHexadecimal(String str) {
    return hexadecimal.hasMatch(str);
  }
  
  
  // check if the string is a hexadecimal color
  bool isHexColor(String str) {
    return hexcolor.hasMatch(str);
  }
  
  
  
negative.code:     }
      return (checksum % 11 == 0);
    } else if (version == '13') {
      if (!_isbn13Maybe.hasMatch(sanitized)) {
        return false;
      }
      var factor = [1, 3];
  