code: @SuppressWarnings("unchecked")
      public static <T> ConnectableObservable<T> createFrom(ObservableSource<? extends T> source) {
          ObservableSource<T> sourceCast = (ObservableSource<T>) source;
          return create(sourceCast, DEFAULT_UNBOUNDED_FACTORY);
      }
docs: Creates a replaying ConnectableObservable with an unbounded buffer.
  @param <T> the value type
  @param source the source observable
  @return the new ConnectableObservable instance