src/main/java/io/reactivex/internal/operators/observable/ObservableReplay.java
@SuppressWarnings("unchecked")
    public static <T> ConnectableObservable<T> createFrom(ObservableSource<? extends T> source) {
        return create(source, DEFAULT_UNBOUNDED_FACTORY);
    }
@SuppressWarnings("unchecked")
    public static <T> ConnectableObservable<T> createFrom(ObservableSource<? extends T> source) {
        return create(source, DEFAULT_UNBOUNDED_FACTORY);
    }
Creates a replaying ConnectableObservable with an unbounded buffer.
@param <T> the value type
@param source the source observable
@return the new ConnectableObservable instance