/**
 * Observable.combineLatest(List<? extends Observable<? extends T>> sources, FuncN<? extends R> combineFunction)
 * kotlin sugar variant
 */
@Suppress("UNCHECKED_CAST")
fun <T, R> List<Observable<T>>.combineLatest(combineFunction: (args: List<T>) -> R): Observable<R> =
        Observable.combineLatest(this, { combineFunction(it.map { it as T }) })