code: func (v *TreeModel) GetValue(iter *TreeIter, column int) (*glib.Value, error) {
  	val, err := glib.ValueAlloc()
  	if err != nil {
  		return nil, err
  	}
  	C.gtk_tree_model_get_value(
  		(*C.GtkTreeModel)(unsafe.Pointer(v.native())),
  		iter.native(),
  		C.gint(column),
  		(*C.GValue)(unsafe.Pointer(val.Native())))
  	return val, nil
  }
docs: // GetValue() is a wrapper around gtk_tree_model_get_value().