public static <E extends @Nullable Object> Funnel<Iterable<? extends E>> sequentialFunnel(
      Funnel<E> elementFunnel) {
    return new SequentialFunnel<>(elementFunnel);
  }

  private static class SequentialFunnel<E extends @Nullable Object>
      implements Funnel<Iterable<? extends E>>, Serializable {
    private final Funnel<E> elementFunnel;

    SequentialFunnel(Funnel<E> elementFunnel) {

        .addEqualityGroup(Funnels.stringFunnel(Charsets.US_ASCII))
        .addEqualityGroup(
            Funnels.sequentialFunnel(Funnels.integerFunnel()),
            SerializableTester.reserialize(Funnels.sequentialFunnel(Funnels.integerFunnel())))
        .addEqualityGroup(Funnels.sequentialFunnel(Funnels.longFunnel()))
        .testEquals();
  }

        .addEqualityGroup(Funnels.stringFunnel(Charsets.US_ASCII))
        .addEqualityGroup(
            Funnels.sequentialFunnel(Funnels.integerFunnel()),
            SerializableTester.reserialize(Funnels.sequentialFunnel(Funnels.integerFunnel())))
        .addEqualityGroup(Funnels.sequentialFunnel(Funnels.longFunnel()))
        .testEquals();
  }