private class ListIteratorImpl implements ListIterator<T> {
        private final ListIterator<T> iterator;
        private T lastElement;

        public ListIteratorImpl(ListIterator<T> iterator) {
            this.iterator = iterator;
        }

        @Override
        public boolean hasNext() {
            return iterator.hasNext();
        }

        @Override
        public boolean hasPrevious() {

  /** Support for {@link Iterator#remove()}. */
  SUPPORTS_REMOVE,
  /**
   * Support for {@link ListIterator#add(Object)}; ignored for plain {@link Iterator}
   * implementations.
   */
  SUPPORTS_ADD,
  /**
   * Support for {@link ListIterator#set(Object)}; ignored for plain {@link Iterator}
   * implementations.
   */
  SUPPORTS_SET;

  /**

      @Override
      SortedMultiset<E> forwardMultiset() {
        return AbstractSortedMultiset.this;
      }

      @Override
      Iterator<Entry<E>> entryIterator() {
        return descendingEntryIterator();
      }

      @Override
      public Iterator<E> iterator() {
        return descendingIterator();
      }
    }
    return new DescendingMultisetImpl();
  }

      @Override
      SortedMultiset<E> forwardMultiset() {
        return AbstractSortedMultiset.this;
      }

      @Override
      Iterator<Entry<E>> entryIterator() {
        return descendingEntryIterator();
      }

      @Override
      public Iterator<E> iterator() {
        return descendingIterator();
      }
    };
  }

  /** Support for {@link Iterator#remove()}. */
  SUPPORTS_REMOVE,
  /**
   * Support for {@link ListIterator#add(Object)}; ignored for plain {@link Iterator}
   * implementations.
   */
  SUPPORTS_ADD,
  /**
   * Support for {@link ListIterator#set(Object)}; ignored for plain {@link Iterator}
   * implementations.
   */
  SUPPORTS_SET;

  /**

        and:
        source.iterator().collect() == ["foo", "bar"]
    }

    def "can re-add an ordinary value after removal"() {
        when:
        source.add("a")
        source.add("b")
        source.remove("a")

        then:
        source.iterator().collect() == ["b"]

        when:
        source.add("a")

        then:
        source.iterator().collect() == ["b", "a"]
    }

        @Override
        N visitNext(Deque<Iterator<? extends N>> horizon) {
          Iterator<? extends N> top = horizon.getFirst();
          if (top.hasNext()) {
            return checkNotNull(top.next());
          }
          horizon.removeFirst();
          return null;
        }
      };
    }

    final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) {

        @Override
        N visitNext(Deque<Iterator<? extends N>> horizon) {
          Iterator<? extends N> top = horizon.getFirst();
          if (top.hasNext()) {
            return checkNotNull(top.next());
          }
          horizon.removeFirst();
          return null;
        }
      };
    }

    final Iterator<N> breadthFirst(Iterator<? extends N> startNodes) {

        then:
        selectors.size() == 2
        selectors.first() == selector1

        when:
        def iterator = selectors.iterator()

        then:
        iterator.next() == selector1
        iterator.next() == selector2
        !iterator.hasNext()
    }

    def 'when adding 2 selectors and one dynamic, non-dynamic is first'() {
        given:

    private static final ImmutableSet<Integer> INTEGERS = ImmutableSet.of(1, 2, 3, 4);
    private final Iterator<Integer> iterator;

    public IterableIterator() {
      this.iterator = iterator();
    }

    @Override
    public Iterator<Integer> iterator() {
      return INTEGERS.iterator();
    }

    @Override