anchor.diff:    /// [SemanticsNode]s.
     ///
     /// See also:
  +  ///
     ///  * [addTagForChildren] to add a tag and for more information about their
     ///    usage.
     Iterable<SemanticsTag> get tagsForChildren => _tagsForChildren;
  
positive.code:   /// decedent nodes are merged into this node.
    ///
    /// See also:
    ///  * [isMergedIntoParent]
    ///  * [mergeAllDescendantsIntoThisNode]
    bool get isPartOfNodeMerging => mergeAllDescendantsIntoThisNode || isMergedIntoParent;
  
negative.code:   /// registered.
    ///
    /// See also:
    ///
    ///  * [addAction] to add an action.
    VoidCallback getActionHandler(SemanticsAction action) => _actions[action];
  
  