TResult - the type of element signaled.public interface Observable<TResult>
Observable represents a MongoDB operation.
 
 As such it is a provider of a potentially unbounded number of sequenced elements, publishing them according to the demand received
 from its Observer(s).
 
Observables| Modifier and Type | Method and Description | 
|---|---|
| void | subscribe(Observer<? super TResult> observer)Request  Observableto start streaming data. | 
void subscribe(Observer<? super TResult> observer)
Observable to start streaming data.
 This is a "factory method" and can be called multiple times, each time starting a new Subscription.
Each Subscription will work for only a single Observer.
 If the Observable rejects the subscription attempt or otherwise fails it will
 signal the error via Observer.onError(java.lang.Throwable).
 
observer - the Observer that will consume signals from this Observable