Programatically opening a folder in a TreeGrid

Per the docmentation of the TreeGrid.addFolderOpenedHandler()
http://www.smartclient.com/smartgwte...OpenedHandler)

It says: "This method is called when a folder is opened either via the user manipulating the expand/collapse control in the UI or via TreeGrid.openFolder."

I do not see TreeGrid.openFolder in the documentation. How do you open/close a folder programatically?