this.iterators = iterators;
    }

    @Override
    public boolean hasNext() {
        for (; index < iterators.length; ++index) {
            if (iterators[index].hasNext()) {
                return true;
            }
        }
        return false;
    }

    @Override
    public E next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }

    }

    @Override
    public boolean hasNext() {
      return !stack.isEmpty();
    }

    @Override
    public T next() {
      Iterator<T> itr = stack.getLast(); // throws NSEE if empty
      T result = checkNotNull(itr.next());
      if (!itr.hasNext()) {
        stack.removeLast();
      }
      Iterator<T> childItr = children(result).iterator();

          int i;

          @Override
          public boolean hasNext() {
            return i < array.length;
          }

          @Override
          public String next() {
            if (!hasNext()) {
              throw new NoSuchElementException();
            }
            return array[i++];
          }
        };

    assertTrue(iterator.hasNext());
    assertEquals("a", iterator.next());
    try {

    assertEquals(rangeSet.asDescendingSetOfRanges().isEmpty(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asRanges().iterator().hasNext(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asDescendingSetOfRanges().iterator().hasNext(), rangeSet.isEmpty());

    List<Range<C>> asRanges = ImmutableList.copyOf(rangeSet.asRanges());

    // test that connected ranges are coalesced

    while (expectedIter.hasNext() && actualIter.hasNext()) {
      if (!equal(expectedIter.next(), actualIter.next())) {
        Assert.fail(
            "contents were not equal and in the same order: "
                + "expected = "
                + expected
                + ", actual = "
                + actual);
      }
    }

    if (expectedIter.hasNext() || actualIter.hasNext()) {

      @CheckForNull K currentKey = null;
      Iterator<V> valueItr = Iterators.emptyIterator();

      @Override
      public boolean hasNext() {
        return valueItr.hasNext() || asMapItr.hasNext();
      }

      @Override
      public Entry<K, V> next() {
        if (!valueItr.hasNext()) {
          Entry<K, ? extends ImmutableCollection<V>> entry = asMapItr.next();
          currentKey = entry.getKey();

  }

  /**
   * Implementation for the EntryIterator, which is used to build Key and Value iterators.
   *
   * <p>Expiration is only checked on hasNext(), so as to ensure that a next() call never returns
   * null when hasNext() has already been called.
   */
  class EntryIterator implements Iterator<Entry<K, V>> {
    Iterator<Entry<K, Timestamped<V>>> iterator;
    Entry<K, Timestamped<V>> lastEntry;

      this.iterator = iterable.iterator();
    }

    @Override
    public boolean hasNext() {
      return true; // pretend that you have more...
    }

    @Override
    public E next() {
      // ...but throw an unchecked exception when you ask for it.
      if (!iterator.hasNext()) {
        throw new ThrowsAtEndException();
      }
      return iterator.next();
    }

          Set<N> seenNodes = new HashSet<>();
          return new AbstractIterator<N>() {
            @Override
            @CheckForNull
            protected N computeNext() {
              while (nodeConnections.hasNext()) {
                NodeConnection<N> nodeConnection = nodeConnections.next();
                boolean added = seenNodes.add(nodeConnection.node);
                if (added) {
                  return nodeConnection.node;

    }

    @Override
    public Iterator<U> iterator() {
        Iterator<V> it = list.iterator();
        return new Iterator<U>() {
            @Override
            public boolean hasNext() {
                return it.hasNext();
            }

            @Override
            public U next() {
                return mapper.apply(it.next());
            }
        };
    }

    @Override