@GwtCompatible
public final class Maps {
  private Maps() {}

  static <K extends @Nullable Object, V extends @Nullable Object> Iterator<K> keyIterator(
      Iterator<Entry<K, V>> entryIterator) {
    return new TransformedIterator<Entry<K, V>, K>(entryIterator) {
      @Override
      @ParametricNullness
      K transform(Entry<K, V> entry) {
        return entry.getKey();
      }
    };
  }

      return true;
    } else {
      return false;
    }
  }

  static <E extends @Nullable Object> Iterator<E> elementIterator(
      Iterator<Entry<E>> entryIterator) {
    return new TransformedIterator<Entry<E>, E>(entryIterator) {
      @Override
      @ParametricNullness
      E transform(Entry<E> entry) {
        return entry.getElement();
      }
    };
  }

      return true;
    } else {
      return false;
    }
  }

  static <E extends @Nullable Object> Iterator<E> elementIterator(
      Iterator<Entry<E>> entryIterator) {
    return new TransformedIterator<Entry<E>, E>(entryIterator) {
      @Override
      @ParametricNullness
      E transform(Entry<E> entry) {
        return entry.getElement();
      }
    };
  }

@GwtCompatible
public final class Maps {
  private Maps() {}

  static <K extends @Nullable Object, V extends @Nullable Object> Iterator<K> keyIterator(
      Iterator<Entry<K, V>> entryIterator) {
    return new TransformedIterator<Entry<K, V>, K>(entryIterator) {
      @Override
      @ParametricNullness
      K transform(Entry<K, V> entry) {
        return entry.getKey();
      }
    };
  }

  public static <F extends @Nullable Object, T extends @Nullable Object> Iterator<T> transform(
      Iterator<F> fromIterator, Function<? super F, ? extends T> function) {
    checkNotNull(function);
    return new TransformedIterator<F, T>(fromIterator) {
      @ParametricNullness
      @Override
      T transform(@ParametricNullness F from) {
        return function.apply(from);
      }
    };
  }

  /**

  public static <F extends @Nullable Object, T extends @Nullable Object> Iterator<T> transform(
      Iterator<F> fromIterator, Function<? super F, ? extends T> function) {
    checkNotNull(function);
    return new TransformedIterator<F, T>(fromIterator) {
      @ParametricNullness
      @Override
      T transform(@ParametricNullness F from) {
        return function.apply(from);
      }
    };
  }

  /**

    Keys(Multimap<K, V> multimap) {
      this.multimap = multimap;
    }

    @Override
    Iterator<Multiset.Entry<K>> entryIterator() {
      return new TransformedIterator<Map.Entry<K, Collection<V>>, Multiset.Entry<K>>(
          multimap.asMap().entrySet().iterator()) {
        @Override
        Multiset.Entry<K> transform(Map.Entry<K, Collection<V>> backingEntry) {

    Keys(Multimap<K, V> multimap) {
      this.multimap = multimap;
    }

    @Override
    Iterator<Multiset.Entry<K>> entryIterator() {
      return new TransformedIterator<Map.Entry<K, Collection<V>>, Multiset.Entry<K>>(
          multimap.asMap().entrySet().iterator()) {
        @Override
        Multiset.Entry<K> transform(Map.Entry<K, Collection<V>> backingEntry) {