anchor.diff:    ///
     /// Convenience function to ensure that a [YamlList] is returned.
     ///
  -  /// Throws [ArgumentError] if the element at the given path is not a [YamlList]
  -  /// or if the path is invalid. If [checkAlias] is `true`, and an aliased node
  -  /// is encountered along [path], an [AliasError] will be thrown.
  +  /// Throws [ArgumentError] if the element at the given path is not a
  +  /// [YamlList] or if the path is invalid. If [checkAlias] is `true`, and an
  +  /// aliased node is encountered along [path], an [AliasError] will be thrown.
     YamlList _traverseToList(Iterable<Object> path, {bool checkAlias = false}) {
       ArgumentError.checkNotNull(path, 'path');
       ArgumentError.checkNotNull(checkAlias, 'checkAlias');
  
positive.code:     _performEdit(edit, path, expected);
    }
  
    /// Changes the contents of the list at [path] by removing [deleteCount] items
    /// at [index], and inserting [values] in-place. Returns the elements that
    /// are deleted.
    ///
    /// [index] and [deleteCount] must be non-negative and [index] + [deleteCount]
    /// must be no greater than the list's length.
    ///
    /// Throws a [ArgumentError] if the element at the given path is not a [YamlList]
    /// or if the path is invalid.
    ///
    /// **Example:**
    /// ```dart
  
negative.code: ///
  /// To get to `7`, our path will be `['c', 2, 'f', 1]`. The path for the base
  /// object is the empty array `[]`. All modification methods will throw a
  /// [ArgumentError] if the path provided is invalid. Note also that that the
  /// order of elements in the path is important, and it should be arranged in
  /// order of calling, with the first element being the first key or index to be
  /// called.
  ///
  /// In most modification methods, users are required to pass in a value to be
  /// used for updating the YAML tree. This value is only allowed to either be a
  