* Set<Object> identityHashSet = Sets.newSetFromMap(
   *     new IdentityHashMap<Object, Boolean>());
   * }</pre>
   *
   * <p>The returned set is serializable if the backing map is.
   *
   * @param map the backing map
   * @return the set backed by the map
   * @throws IllegalArgumentException if {@code map} is not empty
   * @deprecated Use {@link Collections#newSetFromMap} instead.
   */
  @Deprecated

import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Synchronized collection views. The returned synchronized collection views are serializable if the
 * backing collection and the mutex are serializable.
 *
 * <p>If {@code null} is passed as the {@code mutex} parameter to any of this class's top-level

   * individual iterator as it is generated.
   *
   * @param iterator the backing iterator. The {@link PeekingIterator} assumes ownership of this
   *     iterator, so users should cease making direct calls to it after calling this method.
   * @return a peeking iterator backed by that iterator. Apart from the additional {@link

      dest.put(entry.getValue(), entry.getKey());
    }
    return dest;
  }

  /**
   * Returns a synchronized (thread-safe) multimap backed by the specified multimap. In order to
   * guarantee serial access, it is critical that <b>all</b> access to the backing multimap is
   * accomplished through the returned multimap.
   *
   * <p>It is imperative that the user manually synchronize on the returned multimap when accessing

   * individual iterator as it is generated.
   *
   * @param iterator the backing iterator. The {@link PeekingIterator} assumes ownership of this
   *     iterator, so users should cease making direct calls to it after calling this method.
   * @return a peeking iterator backed by that iterator. Apart from the additional {@link

 * {@code CaffeinatedGuava} adapter class</a>, which lets you build a Guava {@code Cache} or a Guava
 * {@code LoadingCache} backed by a Guava {@code CacheLoader}.
 *
 * <p>Caffeine's API for asynchronous operations uses {@code CompletableFuture}: <a