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 myfunc(first, second=None, third=Optional(5), fourth=Optional(execute=list)):
            #Equivalent: second = deoption(second, 5)
            if isinstance(second, type(None)):
                second = 5