+static gint tree_model_n_children (GtkTreeModel *tree_model,
+ GtkTreeIter *iter);
+
+static gboolean tree_model_iter_children (GtkTreeModel *,
+ GtkTreeIter *,
+ GtkTreeIter *);
+
+static gboolean tree_model_iter_parent (GtkTreeModel *tree_model,
+ GtkTreeIter *iter,
+ GtkTreeIter *child);
+
+static gboolean tree_model_iter_has_child (GtkTreeModel *tree_model,
+ GtkTreeIter *iter);