docs: public static <A> Iterable<Pair<Integer, A>> indexed(final Iterable<? extends A> iterable) {
  		if (iterable == null)
  			throw new NullPointerException("iterable");
  		return new Iterable<Pair<Integer, A>>() {
  			@Override
  			public Iterator<Pair<Integer, A>> iterator() {
  				return IteratorExtensions.indexed(iterable.iterator());
  			}
  		};
  	}