How to get item parent in a Tree?

Hi all!

Could you pls. explain how to work with Tree?

For example I have created Tree and some items in it.

But if I try to get parent or treeItems - all time I have warnings: *WARNING* hiGetTree: bad tree item description.
On the forum I found how to get description, in this case we must use: eval(item)->description. But how we can get parent of item?
For example I want to see treeItems, I type: dprint(hiGetTreeItems(catTree))

and in result: 

*WARNING* hiGetTreeItems: bad tree description.
hiGetTreeItems(catTree) = nil

foreach(item selItems
   dprint(eval(item)->??)
   println(hiGetTree(item))
);

(eval(item)->??) = (_expandedSelectionIcon nil _expandedIcon nil _activeUT _description ("-----" "pcell DRC") _selectionIcon nil _labelIcon nil hiFieldSym backSubItem1)
*WARNING* hiGetTree: bad tree item description.

foreach(item selItems
println(hiGetTreeParent(item))
);

*WARNING* hiGetTreeParent: bad tree description.
nil

And the same situation with expand, by default all items in the tree are collapsed, I try to expand it  hiExpandTreeItem(item t); but without results