def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def is_active(self):
        """
        Returns True when the start date is today or in the past and the
        task has not yet been completed.
        """
        start = self.start_date()
        return not self.is_completed() and (not start or start <= date.today())