private void OnSyntacticalCoverTreeRowActivated(object sender,
                                                 RowActivatedArgs args)
 {
     if (syntacticalCoverTree.GetRowExpanded(args.Path))
     {
         syntacticalCoverTree.CollapseRow(args.Path);
     }
     else
     {
         syntacticalCoverTree.ExpandRow(args.Path, true);
     }
 }