anchor.diff:              let path = selected.[0]
               let _res, iterOriginal = getIter path
               path.Down()
  -            let nodes = getSelectedNodes pad
  +            let node = getSelectedNode pad
               let res, iter = getIter path
  -            if res && nodes.[0].Expanded then
  +            if res && node.Expanded then
                   select tree iter
               else
                   let path = getPath tree
  
positive.code:             let res, iter = getIter path
              if prev && res then
                  select tree iter
                  let nodes = getSelectedNodes pad
                  if nodes.[0].Expanded then
                      // move to last child
                      let path = getPath tree
                      path.Down()
  
negative.code:         tree.Selection.UnselectAll()
          tree.Selection.SelectIter iter.Value
  
      let getSelectedNode (pad:TreeViewPad) =
          let (node:ITreeNavigator) = pad.TreeView?GetSelectedNode()
          node
  
      let getPath (tree:TreeView) =
          tree.Selection.GetSelectedRows().[0]
  