def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def __init__(self, config_d, path=None, resolver=None):
        super().__init__(path=path, resolver=resolver)
        self._collection = {}
        for key, value in config_d.items():
            self._collection[key] = self._from_python(key, value)