*
   * @deprecated instances of {@code FluentIterable} don't need to be converted to {@code
   *     FluentIterable}
   */
  @Deprecated
  @InlineMe(
      replacement = "checkNotNull(iterable)",
      staticImports = {"com.google.common.base.Preconditions.checkNotNull"})
  public static <E extends @Nullable Object> FluentIterable<E> from(FluentIterable<E> iterable) {
    return checkNotNull(iterable);
  }

  /**

   * already a {@code FluentIterable}.
   *
   * <p><b>{@code Stream} equivalent:</b> {@link Collection#stream} if {@code iterable} is a {@link
   * Collection}; {@link Streams#stream(Iterable)} otherwise.
   */
  public static <E extends @Nullable Object> FluentIterable<E> from(final Iterable<E> iterable) {
    return (iterable instanceof FluentIterable)
        ? (FluentIterable<E>) iterable

    FluentIterable<TimeUnit> unused =
        FluentIterable.from(TimeUnit.values()).append(TimeUnit.SECONDS);
  }

  public void testFromArrayAndIteratorRemove() {
    FluentIterable<TimeUnit> units = FluentIterable.from(TimeUnit.values());
    try {
      Iterables.removeIf(units, Predicates.equalTo(TimeUnit.SECONDS));
      fail("Expected an UnsupportedOperationException to be thrown but it wasn't.");

    FluentIterable<TimeUnit> unused =
        FluentIterable.from(TimeUnit.values()).append(TimeUnit.SECONDS);
  }

  public void testFromArrayAndIteratorRemove() {
    FluentIterable<TimeUnit> units = FluentIterable.from(TimeUnit.values());
    try {
      Iterables.removeIf(units, Predicates.equalTo(TimeUnit.SECONDS));
      fail("Expected an UnsupportedOperationException to be thrown but it wasn't.");

    assertThat(onlyPresent).containsExactly(2);
  }

  private static Optional<Integer> getSomeOptionalInt() {
    return Optional.of(1);
  }

  private static FluentIterable<? extends Number> getSomeNumbers() {
    return FluentIterable.from(ImmutableList.<Number>of());
  }

  /*
   * The following tests demonstrate the shortcomings of or() and test that the casting workaround

  public static <E> Iterable<E> unmodifiableIterable(ImmutableCollection<E> iterable) {
    return checkNotNull(iterable);
  }

  private static final class UnmodifiableIterable<T extends @Nullable Object>
      extends FluentIterable<T> {
    private final Iterable<? extends T> iterable;

    private UnmodifiableIterable(Iterable<? extends T> iterable) {
      this.iterable = iterable;
    }

    @Override

    assertThat(onlyPresent).containsExactly(2);
  }

  private static Optional<Integer> getSomeOptionalInt() {
    return Optional.of(1);
  }

  private static FluentIterable<? extends Number> getSomeNumbers() {
    return FluentIterable.from(ImmutableList.<Number>of());
  }

  /*
   * The following tests demonstrate the shortcomings of or() and test that the casting workaround

   * @deprecated Use {@link com.google.common.graph.Traverser#depthFirstPreOrder} instead, which has
   *     the same behavior.
   */
  @Deprecated
  public final FluentIterable<T> preOrderTraversal(final T root) {
    checkNotNull(root);
    return new FluentIterable<T>() {
      @Override
      public UnmodifiableIterator<T> iterator() {
        return preOrderIterator(root);
      }
    };
  }

    checkNotNull(annotationType);
    return FluentIterable.from(annotations).filter(annotationType).first().orNull();
  }

  /**
   * @since 18.0
   */
  @Override
  public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationType) {
    @Nullable
    A[] result = FluentIterable.from(annotations).filter(annotationType).toArray(annotationType);

  public static <E> Iterable<E> unmodifiableIterable(ImmutableCollection<E> iterable) {
    return checkNotNull(iterable);
  }

  private static final class UnmodifiableIterable<T extends @Nullable Object>
      extends FluentIterable<T> {
    private final Iterable<? extends T> iterable;

    private UnmodifiableIterable(Iterable<? extends T> iterable) {
      this.iterable = iterable;
    }

    @Override