def subscribe(self, on_next=None, on_error=None, on_completed=None,
                  observer=None):

        # Be forgiving and accept an un-named observer as first parameter
        if isinstance(on_next, AbstractObserver):
            observer = on_next
        elif not observer:
            observer = Observer(on_next, on_error, on_completed)

        return self._subscribe(observer)
Subscribes an observer to the observable sequence. Returns the
dataset/ETHPy150Open ReactiveX/RxPY/rx/observable.py/Observable.subscribe