Lets the tree ref the node.
- an object of type Gtk.TreeIter
This is an optional method for models to implement. To be more specific, models may ignore this call as it exists primarily for performance reasons.
This function is primarily meant as a way for views to let caching models know when nodes are being displayed (and hence, whether or not to cache that node.) For example, a file-system based model would not want to keep the entire file-hierarchy in memory, just the sections that are currently being displayed by every current view.
A model should be expected to be able to get an iter independent of its referenced state.