def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def json_usage(root):
    root = os.path.abspath(root)
    result = [['Path', 'Parent', 'Usage']]
    result.extend(entry for entry in usage_iter(root))
    return json.dumps(result)