Indicator想要同时存在几个，然后各自关闭各自的Indicator

Indicator现在好像是单例模式，我在请求API之前使用Indicator.open()，在API返回结果之后使用Indicator.close()，但是针对同时请求多个API的情况，Indicator.close()一次就把所有Indicator全部关闭了。
希望能提供一个解决方案，比如Indicator.open()可以返回一个Indicator对象，这样方便每个Indicator对象自己管控自己。

Start by locating the Indicator implementation and its open() and close() entry points, then review how concurrent API requests use them. Done means multiple indicators can coexist and each can be closed independently without closing the others; add or update coverage for that behavior if the existing project structure provides a relevant test location.

Written by the indexing model from the issue text.