### Question:
TransformingObservables { @NonNull public static Observable<Integer> parallel() { Observable<Integer> first = Observable.just(1, 4, 8); Observable<Integer> second = Observable.just(2, 6, 9); Observable<Integer> third = Observable.just("Red", "Hello").map(String::length); return Observable.merge(first, second, third); }  @NonNull static Observable<Integer> sequential(); @NonNull static Observable<Integer> parallel(); @NonNull static Observable<Person> zipPersons();  }### Answer:
@Test public void testParallel() throws Exception { assertNotNull(TransformingObservables.parallel()); }