SettableFuture<Foo> f1 = SettableFuture.create();
    final SettableFuture<Bar> secondary = SettableFuture.create();
    AsyncFunction<Foo, Bar> function =
        new AsyncFunction<Foo, Bar>() {
          @Override
          public ListenableFuture<Bar> apply(Foo unused) {
            return secondary;
          }
        };
    ListenableFuture<Bar> f2 = transformAsync(f1, function, directExecutor());
    f1.cancel(true);