anchor.diff:    ///
     /// The list contains the strings returned by [group] for each index in
     /// [groupIndices].
  +  /// ```dart import dart:convert
  +  ///
  +  /// final string = '[00:13.37] This is a chat message.';
  +  /// final regExp = RegExp(r'^\[\s*(\d+):(\d+)\.(\d+)\]\s*(.*)$');
  +  /// final match = regExp.firstMatch(string)!;
  +  /// final message = jsonEncode(match.groups([1, 2, 3, 4]));
  +  /// // ['00','13','37','This is a chat message.']
  +  /// ```
     List<String?> groups(List<int> groupIndices);
   
     /// Returns the number of captured groups in the match.
  
positive.code: /// The following example finds all matches of a [RegExp] in a [String]
  /// and iterates through the returned iterable of `Match` objects.
  /// ```dart
  /// RegExp exp = RegExp(r"(\w+)");
  /// String str = "Parse my string";
  /// Iterable<Match> matches = exp.allMatches(str);
  /// for (Match m in matches) {
  ///   String match = m[0]!;
  ///   print(match);
  /// }
  
negative.code:   ///
    /// The result may be `null` if the pattern didn't assign a value to it
    /// as part of this match.
    /// ```dart import dart:convert
    ///
    /// final string = '[00:13.37] This is a chat message.';
    /// final regExp = RegExp(r'^\[\s*(\d+):(\d+)\.(\d+)\]\s*(.*)$');
    /// final match = regExp.firstMatch(string)!;
    /// final message = jsonEncode(match[0]!); // '[00:13.37] This is a chat message.'
    /// final hours = jsonEncode(match[1]!); // '00'
    /// final minutes = jsonEncode(match[2]!); // '13'
    /// final seconds = jsonEncode(match[3]!); // '37'
    /// final text = jsonEncode(match[4]!); // 'This is a chat message.'
    /// ```
    String? group(int group);
  
    /// The string matched by the given [group].
  