| io.reactivex.ObservableTransformer<Upstream, Downstream> | 
Interface to compose Observables.
| Public Methods | |||||||||||
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| abstract ObservableSource<Downstream> | apply(Observable<Upstream> upstream) Applies a function to the upstream Observable and returns an ObservableSource with
 optionally different element type. | ||||||||||
Applies a function to the upstream Observable and returns an ObservableSource with optionally different element type.
| upstream | the upstream Observable instance | 
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