@GwtCompatible
public enum MapFeature implements Feature<Map> {
  /**
   * The map does not throw {@code NullPointerException} on calls such as {@code containsKey(null)},
   * {@code get(null)}, {@code keySet().contains(null)} or {@code remove(null)}.
   */
  ALLOWS_NULL_KEY_QUERIES,
  ALLOWS_NULL_KEYS(ALLOWS_NULL_KEY_QUERIES),
  /**
   * The map does not throw {@code NullPointerException} on calls such as {@code

    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public Set<K> keySet() {
      /*
       * We can't use StandardKeySet, as NavigableMapTestSuiteBuilder assumes that our keySet is a
       * NavigableSet. We test StandardKeySet in the superclass, so it's still covered.
       */
      return navigableKeySet();
    }

    @Override

  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,

  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  private SafeTreeMap(NavigableMap<K, V> delegate) {
    this.delegate = checkNotNull(delegate);
    for (K k : keySet()) {
      checkValid(k);
    }
  }

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

  @Override

 * ListMultimap<String, String> multimap = ArrayListMultimap.create();
 * for (President pres : US_PRESIDENTS_IN_ORDER) {
 *   multimap.put(pres.firstName(), pres.lastName());
 * }
 * for (String firstName : multimap.keySet()) {
 *   List<String> lastNames = multimap.get(firstName);
 *   out.println(firstName + ": " + lastNames);
 * }
 * }
 *
 * ... produces output such as:
 *
 * {@snippet :
 * Zachary: [Taylor]

    return Maps.safeContainsKey(columnMap(), columnKey);
  }

  @Override
  public Set<R> rowKeySet() {
    return rowMap().keySet();
  }

  @Override
  public Set<C> columnKeySet() {
    return columnMap().keySet();
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    for (Map<C, V> row : rowMap().values()) {
      if (row.containsValue(value)) {

    return Maps.safeContainsKey(columnMap(), columnKey);
  }

  @Override
  public Set<R> rowKeySet() {
    return rowMap().keySet();
  }

  @Override
  public Set<C> columnKeySet() {
    return columnMap().keySet();
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    for (Map<C, V> row : rowMap().values()) {
      if (row.containsValue(value)) {

    return delegate().tailMap(fromKey);
  }

  /**
   * A sensible implementation of {@link SortedMap#keySet} in terms of the methods of {@code
   * ForwardingSortedMap}. In many cases, you may wish to override {@link
   * ForwardingSortedMap#keySet} to forward to this implementation or a subclass thereof.
   *
   * @since 15.0
   */

    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().keySet().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testValuesClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();

    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();
    getMap().keySet().clear();
    assertTrue(getMap().isEmpty());
    assertTrue(inv.isEmpty());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testValuesClearClearsInverse() {
    BiMap<V, K> inv = getMap().inverse();