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 test_vice_versa(self):
        class First(Structure):
            pass
        class Second(Structure):
            pass

        First._fields_ = [("second", Second)]

        try:
            Second._fields_ = [("first", First)]
        except AttributeError as details:
            self.assertTrue("_fields_ is final" in
                            str(details))
        else:
            self.fail("AttributeError not raised")