code: public static <E> Optional<E> maybeLast(Iterable<E> iterable) {
          dbc.precondition(iterable != null, "cannot call maybeLast with a null iterable");
          return new MaybeLastElement<E>().apply(iterable.iterator());
      }
docs: Yields the last element if present, nothing otherwise.
  
  @param <E> the iterable element type
  @param iterable the iterable that will be consumed
  @return the last element or nothing