import java.util.Comparator;
import java.util.SortedSet;
import org.jspecify.annotations.Nullable;

/**
 * A sorted set multimap which forwards all its method calls to another sorted set multimap.
 * Subclasses should override one or more methods to modify the behavior of the backing multimap as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

    initMultimapWithNullKey();
    assertTrue(multimap().keySet().contains(null));
  }

  @MapFeature.Require(ALLOWS_NULL_KEY_QUERIES)
  public void testKeySetContainsNullKeyAbsent() {
    assertFalse(multimap().keySet().contains(null));
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeySetRemovePropagatesToMultimap() {
    int key0Count = multimap().get(k0()).size();

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllAbsentKey() {
    assertEmpty(multimap().removeAll(k3()));
    expectUnchanged();
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllPresentKey() {
    assertContentsAnyOrder(multimap().removeAll(k0()), v0());
    expectMissing(e0());
  }

    super(allowsNulls, allowsNulls, false, modifiable, modifiable, supportsIteratorRemove);
  }

  protected void populate(Multimap<String, Integer> multimap) {
    multimap.put("one", 1);
    multimap.put("two", 2);
    multimap.put("two", 22);
    multimap.put("three", 3);
    multimap.put("three", 33);
    multimap.put("three", 333);
  }

  @Override
  protected String getKeyNotInPopulatedMap() throws UnsupportedOperationException {

  public void testAsMapValuesImplementList() {
    for (Collection<V> valueCollection : multimap().asMap().values()) {
      assertTrue(valueCollection instanceof List);
    }
  }

  public void testAsMapGetImplementsList() {
    for (K key : multimap().keySet()) {
      assertTrue(multimap().asMap().get(key) instanceof List);
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)

  public void testAsMapValuesImplementList() {
    for (Collection<V> valueCollection : multimap().asMap().values()) {
      assertTrue(valueCollection instanceof List);
    }
  }

  public void testAsMapGetImplementsList() {
    for (K key : multimap().keySet()) {
      assertTrue(multimap().asMap().get(key) instanceof List);
    }
  }

  @MapFeature.Require(SUPPORTS_REMOVE)

 *
 * <h2>Collection types</h2>
 *
 * <dl>
 *   <dt>{@link Multimap}
 *   <dd>A new type, which is similar to {@link java.util.Map}, but may contain multiple entries
 *       with the same key. Some behaviors of {@link Multimap} are left unspecified and are provided
 *       only by the subtypes mentioned below.
 *   <dt>{@link ListMultimap}
 *   <dd>An extension of {@link Multimap} which permits duplicate entries, supports random access of

/**
 * Implementation of {@link Multimaps#filterKeys(Multimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
class FilteredKeyMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimap<K, V> implements FilteredMultimap<K, V> {
  final Multimap<K, V> unfiltered;
  final Predicate<? super K> keyPredicate;

/**
 * Implementation of {@link Multimaps#filterKeys(Multimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
class FilteredKeyMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimap<K, V> implements FilteredMultimap<K, V> {
  final Multimap<K, V> unfiltered;
  final Predicate<? super K> keyPredicate;

 *
 * <h2>Collection types</h2>
 *
 * <dl>
 *   <dt>{@link Multimap}
 *   <dd>A new type, which is similar to {@link java.util.Map}, but may contain multiple entries
 *       with the same key. Some behaviors of {@link Multimap} are left unspecified and are provided
 *       only by the subtypes mentioned below.
 *   <dt>{@link ListMultimap}
 *   <dd>An extension of {@link Multimap} which permits duplicate entries, supports random access of