forkJoin7<A, B, C, D, E, F, G, T>  static method 
Merges the given Streams into a single Stream sequence by using the
combiner function when all of the stream sequences emits their
last item.
Example
Rx.forkJoin7(
  Stream.value('a'),
  Stream.value('b'),
  Stream.value('c'),
  Stream.value('d'),
  Stream.value('e'),
  Stream.value('f'),
  Stream.fromIterable(['g', 'h']),
  (a, b, c, d, e, f, g) => a + b + c + d + e + f + g)
.listen(print); //prints 'abcdefh'
Implementation
static Stream<T> forkJoin7<A, B, C, D, E, F, G, T>(
        Stream<A> streamA,
        Stream<B> streamB,
        Stream<C> streamC,
        Stream<D> streamD,
        Stream<E> streamE,
        Stream<F> streamF,
        Stream<G> streamG,
        T Function(A a, B b, C c, D d, E e, F f, G g) combiner) =>
    ForkJoinStream.combine7(streamA, streamB, streamC, streamD, streamE,
        streamF, streamG, combiner);