anchor.diff:    /// // Generate an HmacSecretKey.
     /// final key = await HmacSecretKey.generateKey(sha256);
     ///
  -  /// // Function that creates a stream of data from our string-to-sign:
     /// String stringToSign = 'example-string-to-signed';
  -  /// Stream<List<int>> dataStream() async* {
  -  ///   yield utf8.encode(stringToSign);
  -  /// }
     ///
     /// // Compute signature.
  -  /// final signature = await key.sign(dataStream());
  +  /// final signature = await key.sign(Stream.fromIterable([
  +  ///   utf8.encode(stringToSign),
  +  /// ]));
     ///
     /// // Verify signature.
  -  /// final result = await key.verify(signature, dataStream());
  +  /// final result = await key.verify(signature, Stream.fromIterable([
  +  ///   utf8.encode(stringToSign),
  +  /// ]));
     /// assert(result == true, 'this signature should be valid');
     /// ```
     Future<bool> verify(List<int> signature, Stream<List<int>> data);
  
positive.code:   /// import 'dart:convert' show base64, utf8;
    /// import 'package:webcrypto/webcrypto.dart';
    ///
    /// // Compute hash of the dataStream with sha-256
    /// List<int> hash = await sha256.digest(
    ///   Stream.fromIterable([
    ///     // In this case our stream contains a single chunk of bytes.
  
negative.code:   ///
    /// // Create a signature for UTF-8 encoded message
    /// final message = 'hello world';
    /// final signature = await privateKey.sign(Stream.fromIterable([
    ///   utf8.encode(message),
    /// ])),
    ///
    /// print('signature: ${base64.encode(signature)}');
    /// ```
    Future<Uint8List> sign(Stream<List<int>> data);
  