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_clusters(self):
        """!
        @return (list) Allocated clusters where each cluster is represented by list of indexes of points from dataset,
                        for example, two cluster may have following representation [[0, 1, 4], [2, 3, 5, 6]].