return valueList;
  }

  @Override
  ImmutableCollection<V> createValues() {
    throw new AssertionError("should never be called");
  }

  /**
   * Returns the comparator that orders the keys, which is {@link Ordering#natural()} when the
   * natural ordering of the keys is used. Note that its behavior is not consistent with {@link
   * TreeMap#comparator()}, which returns {@code null} to indicate natural ordering.

            // all the tasks, then the thread will block waiting for all
            // those subtasks to finish.
            // This ensures the number of running workers is no more than
            // the defined parallism, while making sure the pool will not
            // be exhausted
            //
            return new ThreadPoolExecutor(

    return valueList;
  }

  @Override
  ImmutableCollection<V> createValues() {
    throw new AssertionError("should never be called");
  }

  /**
   * Returns the comparator that orders the keys, which is {@link Ordering#natural()} when the
   * natural ordering of the keys is used. Note that its behavior is not consistent with {@link
   * TreeMap#comparator()}, which returns {@code null} to indicate natural ordering.

   * <p>Usage example:
   *
   * <pre>{@code
   * ListenableFuture<Integer> fetchCounterFuture = ...;
   *
   * // Falling back to a zero counter in case an exception happens when
   * // processing the RPC to fetch counters.
   * ListenableFuture<Integer> faultTolerantFuture = Futures.catching(
   *     fetchCounterFuture, FetchException.class, x -> 0, directExecutor());
   * }</pre>
   *