def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def split_container(container, iter):
	root = Tree(container)
	if iter != 0:
		sr = random_split(container)
		if sr!=None:
			root.lchild = split_container(sr[0], iter-1)
			root.rchild = split_container(sr[1], iter-1)
	return root