private Iterables() {}

  /** Returns an unmodifiable view of {@code iterable}. */
  public static <T extends @Nullable Object> Iterable<T> unmodifiableIterable(
      Iterable<? extends T> iterable) {
    checkNotNull(iterable);
    if (iterable instanceof UnmodifiableIterable || iterable instanceof ImmutableCollection) {
      @SuppressWarnings("unchecked") // Since it's unmodifiable, the covariant cast is safe

  private Iterables() {}

  /** Returns an unmodifiable view of {@code iterable}. */
  public static <T extends @Nullable Object> Iterable<T> unmodifiableIterable(
      Iterable<? extends T> iterable) {
    checkNotNull(iterable);
    if (iterable instanceof UnmodifiableIterable || iterable instanceof ImmutableCollection) {
      @SuppressWarnings("unchecked") // Since it's unmodifiable, the covariant cast is safe

    Iterable<String> iterable = Iterables.unmodifiableIterable(list);
    Iterable<String> iterable2 = Iterables.unmodifiableIterable(iterable);
    assertThat(iterable2).isSameInstanceAs(iterable);
    ImmutableList<String> immutableList = ImmutableList.of("a", "b", "c");
    assertThat(Iterables.unmodifiableIterable(immutableList)).isSameInstanceAs(immutableList);
    assertThat(Iterables.unmodifiableIterable((List<String>) immutableList))