def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def chart_title(self):
        """Returns a title for the chart."""
        if self.field:
            return 'Top filtered results for "{0:s}"'.format(self.field)
        return 'Top results for an unknown field after filtering'