* collected. If you want the original list to be eligible for garbage collection, you should
   * create and use a copy of the sub list (e.g., {@code
   * ImmutableList.copyOf(originalList.subList(...))}).
   */
  @Override
  public ImmutableList<E> subList(int fromIndex, int toIndex) {
    checkPositionIndexes(fromIndex, toIndex, size());
    int length = toIndex - fromIndex;