| id | TreeViewItem ID. | 
| expanded | True expands item. False collapses item. | 
                  bool
        True if item changed expanded state, false if item already had the expanded state.
      
Set a single TreeViewItem to be expanded or collapsed.
| ids | List of item IDs that should be expanded. | 
Set the current expanded TreeViewItems of the TreeView. This will overwrite the previous expanded state.