def insertDomain(self, domain, indegree=0, outdegree=0):
		'''增加一个域名'''
		cur = self.conn.cursor()
		cur.execute("INSERT INTO Domains VALUES (NULL,?,?,?)", (domain, indegree, outdegree))
		# 写入到文件中
		self.conn.commit()
def close_log_streams(self):
        """ Closes all log_stream streams. """
        while self._logging_handlers:
            self._logging_handlers.pop().close()