我的芹菜日志显示此错误：
UserWarning: A node named celery@postr is already using this process mailbox!
Maybe you forgot to shutdown the other node or did not do so properly?
Or if you meant to start multiple nodes on the same host please make sure
you give each node a unique node name!
warnings.warn(W_PIDBOX_IN_USE.format(node=self))
如何关闭其他节点？
PS：有没有办法看到所有当前正在运行的节点？