Unsubscribes a gadget from a channel.

取消订阅到信道的 gadget。

When the manager instance shuts down, it unsubscribes from the DataPower devices.

管理程序实例关闭时，它取消DataPower设备订阅。

After the first subscriber subscribes, when messages are published to the topic, the publication point adds the messages to the topic space until the last subscriber unsubscribes.

第一个订户订阅后，发布点会在消息发布到主题时将其添加到主题空间，直到最后一个订户取消订阅为止。