void gtk_tree_list_row_set_expanded ( GtkTreeListRow* self, gboolean expanded )
Expands or collapses a row.
If a row is expanded, the model of calling the
GtkTreeListModelCreateModelFunc for the row’s
item will be inserted after this row. If a row is collapsed,
those items will be removed from the model.
If the row is not expandable, this function does nothing.