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 get_date(self, p_tag):
        """ Given a date tag, return a date object. """
        string = self.tag_value(p_tag)
        result = None

        try:
            result = date_string_to_date(string) if string else None
        except ValueError:
            pass

        return result