def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def paint(self, c):
		self.leaf.paint(c)
		if self.lchild != None:
			self.lchild.paint(c)
		if self.rchild != None:
			self.rchild.paint(c)