docs: public <U> FutureStream<U> fromAdapter(final Adapter<U> adapter) {
          final Subscription sub = new Subscription();
          return new FutureStreamImpl(this,()->adapter.stream(sub)){
              @Override
              public ReactiveSeq<U> stream() {
                  return (ReactiveSeq<U>)adapter.stream(sub);
              }
          };
  
  
      }