code: func (v *TreeModel) FilterNew(root *TreePath) (*TreeModelFilter, error) {
  	c := C.gtk_tree_model_filter_new(v.native(), root.native())
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	obj := glib.Take(unsafe.Pointer(c))
  	return wrapTreeModelFilter(obj), nil
  }
docs: // FilterNew is a wrapper around gtk_tree_model_filter_new().