code: @SuppressWarnings("unchecked")
      public static <T> ConnectableFlowable<T> createFrom(Flowable<? extends T> source) {
          Flowable<T> sourceCast = (Flowable<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 Publisher to use
  @return the new ConnectableObservable instance