anchor.diff:    ///
     /// Example:
     /// ```dart
  -  /// var pairs = [[1, 2], [3, 4]];
  -  /// var flattened = pairs.expand((pair) => pair).toList();
  -  /// print(flattened); // => [1, 2, 3, 4];
  -  ///
  -  /// var input = [1, 2, 3];
  -  /// var duplicated = input.expand((i) => [i, i]).toList();
  -  /// print(duplicated); // => [1, 1, 2, 2, 3, 3]
  +  /// Iterable<int> count(int n) sync* {
  +  ///   for (var i = 1; i <= n; i++) {
  +  ///     yield i;
  +  ///    }
  +  ///  }
  +  ///
  +  /// var numbers = [1, 3, 0, 2];
  +  /// print(numbers.expand(count)); // (1, 1, 2, 3, 1, 2)
     /// ```
     ///
     /// Equivalent to:
  -  /// ```dart
  +  /// ```
     /// Iterable<T> expand<T>(Iterable<T> toElements(E e)) sync* {
     ///   for (var value in this) {
     ///     yield* toElements(value);
  
positive.code:   /// ```
    /// Example of calculating the sum of an iterable:
    /// ```dart
    /// iterable.reduce((value, element) => value + element);
    /// ```
    E reduce(E combine(E value, E element)) {
      Iterator<E> iterator = this.iterator;
  
negative.code:   /// If more than one matching element is found, throws [StateError].
    /// If no matching element is found, returns the result of [orElse].
    /// If [orElse] is omitted, it defaults to throwing a [StateError].
    ///
    /// Example:
    /// ```dart
    /// final numbers = <int>[2, 2, 10];
    /// var result = numbers.singleWhere((element) => element > 5); // 10
    /// ```
    /// When no matching element is found, the result of calling [orElse] is
    /// returned instead.
    /// ```dart continued
    /// result = numbers.singleWhere((element) => element == 1,
    ///     orElse: () => -1); // -1
    /// ```
    /// There must not be more than one matching element.
    /// ```dart continued
    /// result = numbers.singleWhere((element) => element == 2); // Throws Error.
    /// ```
    E singleWhere(bool test(E element), {E orElse()?}) {
      late E result;
      bool foundMatching = false;
  