}
    return false;
  }

  /**
   * Returns an unmodifiable view of the specified navigable set. This method allows modules to
   * provide users with "read-only" access to internal navigable sets. Query operations on the
   * returned set "read through" to the specified set, and attempts to modify the returned set,
   * whether direct or via its collection views, result in an {@code UnsupportedOperationException}.
   *

      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