return new RowSortedMap();
  }

  @WeakOuter
  private final class RowSortedMap extends RowMap implements SortedMap<R, Map<C, V>> {
    @Override
    public SortedSet<R> keySet() {
      return (SortedSet<R>) super.keySet();
    }

    @Override
    SortedSet<R> createKeySet() {
      return new Maps.SortedKeySet<>(this);
    }

    @Override

  }

  @Override
  SortedMap<K, Collection<V>> backingMap() {
    return (SortedMap<K, Collection<V>>) super.backingMap();
  }

  @Override
  public SortedSet<K> keySet() {
    return (SortedSet<K>) super.keySet();
  }

  @Override
  Set<K> createKeySet() {
    return createMaybeNavigableKeySet();
  }

  }

  @Override
  SortedMap<K, Collection<V>> backingMap() {
    return (SortedMap<K, Collection<V>>) super.backingMap();
  }

  @Override
  public SortedSet<K> keySet() {
    return (SortedSet<K>) super.keySet();
  }

  @Override
  Set<K> createKeySet() {
    return createMaybeNavigableKeySet();
  }

    return new RowSortedMap();
  }

  @WeakOuter
  private final class RowSortedMap extends RowMap implements SortedMap<R, Map<C, V>> {
    @Override
    public SortedSet<R> keySet() {
      return (SortedSet<R>) super.keySet();
    }

    @Override
    SortedSet<R> createKeySet() {
      return new Maps.SortedKeySet<>(this);
    }

    @Override

    } catch (RuntimeException tolerated) {
      // GWT's HashMap.keySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRetainAllNullFromEmpty() {
    try {
      super.testKeySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's HashMap.keySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override

    this(new TreeMap<K, V>(map));
  }

  private SafeTreeMap(NavigableMap<K, V> delegate) {
    this.delegate = delegate;
    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override

    private ArrayMap(ImmutableMap<K, Integer> keyIndex) {
      this.keyIndex = keyIndex;
    }

    @Override
    public Set<K> keySet() {
      return keyIndex.keySet();
    }

    K getKey(int index) {
      return keyIndex.keySet().asList().get(index);
    }

    abstract String getKeyRole();

    @ParametricNullness
    abstract V getValue(int index);

  private final transient RegularImmutableSortedSet<K> keySet;
  private final transient ImmutableList<V> valueList;
  private final transient @Nullable ImmutableSortedMap<K, V> descendingMap;

  ImmutableSortedMap(RegularImmutableSortedSet<K> keySet, ImmutableList<V> valueList) {
    this(keySet, valueList, null);
  }

  ImmutableSortedMap(
      RegularImmutableSortedSet<K> keySet,
      ImmutableList<V> valueList,

  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require({SUPPORTS_PUT, SUPPORTS_REMOVE})
  public void testReplaceNonEmptyValues() {
    List<K> keys = copyToList(multimap().keySet());
    List<V> values = asList(v0(), v2(), v3());

    for (K k : keys) {
      resetContainer();

      int size = multimap().size();
      Collection<V> oldKeyValues = copyToList(multimap().get(k));

    }
  }

  private transient @Nullable ImmutableSortedSet<K> keySet;

  @Override
  public ImmutableSortedSet<K> keySet() {
    ImmutableSortedSet<K> ks = keySet;
    return (ks == null) ? (keySet = createKeySet()) : ks;
  }

  @Override
  ImmutableSortedSet<K> createKeySet() {
    // the keySet() of the delegate is only a Set and TreeMap.navigatableKeySet