}
  }

  /**
   * Returns the result of calling {@link CacheLoader#loadAll}, or null if {@code loader} doesn't
   * implement {@code loadAll}.
   */
  @Nullable Map<K, V> loadAll(Set<? extends K> keys, CacheLoader<? super K, V> loader)
      throws ExecutionException {
    checkNotNull(loader);
    checkNotNull(keys);
    Stopwatch stopwatch = Stopwatch.createStarted();
    Map<K, V> result;