Converts @child_path to a path relative to @tree_model_sort. That is,
@child_path points to a path in the child model. The returned path will
point to the same row in the sorted model. If @child_path isn’t a valid
path on the child model, then %NULL is returned.
Converts @child_path to a path relative to @tree_model_sort. That is, @child_path points to a path in the child model. The returned path will point to the same row in the sorted model. If @child_path isn’t a valid path on the child model, then %NULL is returned.