anchor.diff:  /// Listening on a broadcast stream can be treated as listening on a new stream
   /// containing only the events that have not yet been emitted when the [listen]
   /// call occurs.
  -/// For example, the [first] getter listens to the stream, then returns the first
  +/// For example the [first] getter listens to the stream, then returns the first
   /// event that listener receives.
   /// This is not necessarily the first even emitted by the stream, but the first
   /// of the *remaining* events of the broadcast stream.
  
positive.code:   /// an error without a stack trace.
    ///
    /// An asynchronous error `error` is matched by a test function if
    ///`test(error)` returns true. If [test] is omitted, every error is considered
    /// matching.
    ///
    /// If the error is intercepted, the [onError] function can decide what to do
    /// with it. It can throw if it wants to raise a new (or the same) error,
  
negative.code:   /// The returned stream is a broadcast stream if this stream is.
    /// If a broadcast stream is listened to more than once, each subscription
    /// will individually perform the `test`.
    ///
    /// Example:
    /// ```dart
    /// final stream =
    ///     Stream<int>.periodic(const Duration(seconds: 1), (count) => count)
    ///         .take(10);
    ///
    /// final customStream = stream.where((event) => event > 3 && event <= 6);
    /// customStream.listen(print); // Outputs event values: 4,5,6.
    /// ```
    Stream<T> where(bool test(T event)) {
      return new _WhereStream<T>(this, test);
    }
  