def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def __getattr__(self, name: str) -> Any:
        """Custom __getattr__ to allow access to metrics schema fields."""

        if name not in self._metric_fields:
            raise AttributeError('No field: {} in metrics.'.format(name))

        return self._values[name]