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 _check_sigint_gate_is_correct(self):
        assert (
            self._threads_ignoring_sigint >= 0
        ), "This should never happen, someone must have modified the counter outside of SignalHandler."