def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def draw_paths(c, tree):
	if tree.lchild == None or tree.rchild == None:
		return
	tree.lchild.leaf.draw_path(c, tree.rchild.leaf)
	draw_paths(c, tree.lchild)
	draw_paths(c, tree.rchild)