MutableLiveData<List<Integer>> src = new MutableLiveData<>();
        List<Integer> value = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            value.add(i * 2);
        }
        src.setValue(value);

        LiveData<List<String>> dst = Transformations.switchMap(src, input -> {
            final MutableLiveData<List<String>> mld = new MutableLiveData<>();
            new Thread() {
                @Override
                public void run() {
                    Log.d(TAG, "run " + Thread.currentThread());
                    try {
                        Thread.sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    List<String> list = new ArrayList<>();
                    for (Integer i : input) {
                        list.add("-- " + i + " --");
                    }
                    Log.d(TAG, "run " + Thread.currentThread() + " " + list);
                    mld.postValue(list);
                }
            }.start();
            return mld;
        });
        dst.observe(this, strings -> {
            Log.d(TAG, "onCreate " + Thread.currentThread() + " " + strings);
        });