On non-AmigaOS systems this attribute is only supported for the dataview
backend. When creating a treeview and Treeviewcolumn.Hide is
set to True
, RapaGUI will automatically switch to the dataview backend.
If you don't specify this attribute at creation time but want to set it
later using moai.Set(), you have to explicitly request
a dataview widget by setting the Treeview.ForceMode attribute.