def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
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