Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

    multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

    if (permitsDuplicates) {
      assertEquals(9, multimap.size());
    } else {
      assertEquals(8, multimap.size());
    }

    Multimap<@Nullable String, @Nullable Integer> unmodifiable;

                    multimap.put("foo", 17);
                    multimap.put("bar", 32);
                    multimap.put("foo", 16);
                    multimap =
                        Multimaps.filterKeys(multimap, Predicates.not(Predicates.equalTo("foo")));
                    return Multimaps.filterKeys(
                        multimap, Predicates.not(Predicates.equalTo("bar")));

   */
  @CanIgnoreReturnValue
  boolean putAll(@ParametricNullness K key, Iterable<? extends V> values);

  /**
   * Stores all key-value pairs of {@code multimap} in this multimap, in the order returned by
   * {@code multimap.entries()}.
   *
   * @return {@code true} if the multimap changed
   */
  @CanIgnoreReturnValue
  boolean putAll(Multimap<? extends K, ? extends V> multimap);

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.Map;

/**
 * Test {@link Multimap#asMap()} for a {@link Multimaps#forMap} multimap with {@link
 * MapInterfaceTest}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

    multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

    if (permitsDuplicates) {
      assertEquals(9, multimap.size());
    } else {
      assertEquals(8, multimap.size());
    }

    Multimap<@Nullable String, @Nullable Integer> unmodifiable;

   * Multimaps#asMap(ListMultimap)} instead.
   */
  @Override
  Map<K, Collection<V>> asMap();

  /**
   * Compares the specified object to this multimap for equality.
   *
   * <p>Two {@code ListMultimap} instances are equal if, for each key, they contain the same values
   * in the same order. If the value orderings disagree, the multimaps will not be considered equal.
   *

    return Multimaps.transformValues(
            ArrayListMultimap.<String, Integer>create(), Functions.<Integer>identity())
        .asMap();
  }

  @Override
  protected Map<String, Collection<Integer>> makePopulatedMap() {
    ListMultimap<String, Integer> delegate = ArrayListMultimap.create();
    populate(delegate);

    return Multimaps.transformValues(
            ArrayListMultimap.<String, Integer>create(), Functions.<Integer>identity())
        .asMap();
  }

  @Override
  protected Map<String, Collection<Integer>> makePopulatedMap() {
    ListMultimap<String, Integer> delegate = ArrayListMultimap.create();
    populate(delegate);

                    multimap.put("foo", 17);
                    multimap.put("bar", 32);
                    multimap.put("foo", 16);
                    multimap =
                        Multimaps.filterKeys(multimap, Predicates.not(Predicates.equalTo("foo")));
                    return Multimaps.filterKeys(
                        multimap, Predicates.not(Predicates.equalTo("bar")));