static Scheduler applyRequireNonNull(Function<Callable<Scheduler>, Scheduler> f, Callable<Scheduler> s) {
        Scheduler scheduler = apply(f,s);
        if (scheduler == null) {
            throw new NullPointerException("Scheduler Callable returned null");
        }
        return scheduler;
    }
Removes all handlers and resets the default behavior.
android/android_framework/base/src/main/java/rx2/android/plugins/RxAndroidPlugins.java