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 _read_flow(self, file_name):
        # Return the flow or a tuple with the flow and the valid_flow_mask if _has_builtin_flow_mask is True
        pass