code: public void dispose() {
      forAllObservables(new Consumer<ManagedObservable<?>>() {
        @Override
        public void accept(ManagedObservable<?> managedObservable) {
          managedObservable.dispose();
        }
      });
    }
docs: Disposes all Observables managed by this group. Also clears any references to existing
  {@link Observer} objects in order to avoid leaks. This does not disconnect from the upstream
  Observable, so it can be resumed upon calling {@link #observable(Observer)} if
  needed.