anchor.diff:    }
   
     Map<String, dynamic> buildArguments() {
  -    return new Map<String, dynamic>.from(_parameters)..addAll(<String, dynamic>{
  -      'path': path,
  -    });
  +    return new Map<String, dynamic>.from(_parameters)
  +      ..addAll(<String, dynamic>{
  +        'path': path,
  +      });
     }
   
     Stream<Event> _observe(_EventType eventType) {
  
positive.code:   /// than or equal to the given value, using the given orderBy directive or
    /// priority as default, and optionally only child nodes with a key less
    /// than or equal to the given key.
    Query endAt(dynamic value, { String key }) {
      assert(!_parameters.containsKey('endAt'));
      assert(value is String || value is bool || value is double || value is int);
      final Map<String, dynamic> parameters = <String, dynamic>{ 'endAt': value };
      if (key != null) parameters['endAtKey'] = key;
      return _copyWithParameters(parameters);
    }
  
negative.code: 
  /// Represents a query over the data at a particular location.
  class Query {
    Query._(
        {@required FirebaseDatabase database,
        @required List<String> pathComponents,
        Map<String, dynamic> parameters})
        : _database = database,
          _pathComponents = pathComponents,
          _parameters = parameters ??
              new Map<String, dynamic>.unmodifiable(<String, dynamic>{}),
          assert(database != null);
  
    final FirebaseDatabase _database;
    final List<String> _pathComponents;
  