public ListeningFuture<Void> setMode(final FriendPresence.Mode mode) {
   return executorService.submit(
       new Callable<Void>() {
         @Override
         public Void call() throws Exception {
           setModeImpl(mode);
           return null;
         }
       });
 }
 @Override
 public ListeningFuture<Void> removeFriend(final String id) {
   return executorService.submit(
       new Callable<Void>() {
         @Override
         public Void call() throws Exception {
           removeFriendImpl(id);
           return null;
         }
       });
 }
 @Override
 public ListeningFuture<Void> addNewFriend(final String id, final String name) {
   return executorService.submit(
       new Callable<Void>() {
         @Override
         public Void call() throws Exception {
           addFriendImpl(id, name);
           return null;
         }
       });
 }
 @Override
 public ListeningFuture<Void> logout() {
   return executorService.submit(
       new Callable<Void>() {
         @Override
         public Void call() throws Exception {
           logoutImpl(null);
           return null;
         }
       });
 }