def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def __init__(self, data, amount_clusters, means=None, variances=None, observer=None, tolerance=0.00001, iterations=100):
        """!
        @brief Initializes Expectation-Maximization algorithm for cluster analysis.