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kotlinlang

Basically `subscribeOn` affect all the operation above it, and `observeOn` affect operations below it
e.g. 
```
a.map { b }
.subscribeOn(<http://Schedulers.io|Schedulers.io>())
.map{ c }
.observeOn(Schedulers.computation())
.map { d }
```
`subscribeOn` will change the execution thread of `a`, `.map{ b }` to `io()` 
`.map { c }` will also be on the `IO` thread as nothing changes the thread.
`.map { d }` will be executed on the `computation` thread as affected by `observeOn`
Hope it makes you clear