some_file_path = "large-video-file.mp4"
app = FastAPI()


@app.get("/")
def main():
    def iterfile():  # (1)
        with open(some_file_path, mode="rb") as file_like:  # (2)
            yield from file_like  # (3)

3. Dieses `yield from` weist die Funktion an, über das Ding namens `file_like` zu iterieren. Und dann für jeden iterierten Teil, diesen Teil so zurückzugeben, als wenn er aus dieser Generatorfunktion (`iterfile`) stammen würde.

    Es handelt sich also hier um eine Generatorfunktion, die die „generierende“ Arbeit intern auf etwas anderes überträgt.

  /** Returns an unmodifiable view of {@code iterable}. */
  public static <T extends @Nullable Object> Iterable<T> unmodifiableIterable(
      final 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<T> result = (Iterable<T>) iterable;

  public void testSize0() {
    Iterable<String> iterable = Collections.emptySet();
    assertEquals(0, Iterables.size(iterable));
  }

  public void testSize1Collection() {
    Iterable<String> iterable = Collections.singleton("a");
    assertEquals(1, Iterables.size(iterable));
  }

  public void testSize2NonCollection() {
    Iterable<Integer> iterable =
        new Iterable<Integer>() {
          @Override

   * 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

  }

  public void testCharacterSimpleSplitWithNoDelimiter() {
    String simple = "a,b,c";
    Iterable<String> letters = Splitter.on('.').split(simple);
    assertThat(letters).containsExactly("a,b,c").inOrder();
  }

  public void testCharacterSplitWithDoubleDelimiter() {
    String doubled = "a,,b,c";
    Iterable<String> letters = COMMA_SPLITTER.split(doubled);
    assertThat(letters).containsExactly("a", "", "b", "c").inOrder();

public class MinimalIterableTest extends TestCase {

  public void testOf_empty() {
    Iterable<String> iterable = MinimalIterable.<String>of();
    Iterator<String> iterator = iterable.iterator();
    assertFalse(iterator.hasNext());
    try {
      iterator.next();
      fail();
    } catch (NoSuchElementException expected) {
    }
    try {
      iterable.iterator();
      fail();
    } catch (IllegalStateException expected) {
    }

    public Iterable<UseIterable<? extends Iterable<?>>>
        wildcardOfImplicitBoundedIsSubtypeOfWildcardOfExplicitlyBounded(
            List<UseIterable<?>> withImplicitBounds) {
      return isSubtype(withImplicitBounds);
    }

    @TestSubtype(suppressGetSupertype = true, suppressGetSubtype = true)
    public Iterable<UseSerializableIterable<? extends Iterable<?>>>

  }

  public void testCharacterSimpleSplitWithNoDelimiter() {
    String simple = "a,b,c";
    Iterable<String> letters = Splitter.on('.').split(simple);
    assertThat(letters).containsExactly("a,b,c").inOrder();
  }

  public void testCharacterSplitWithDoubleDelimiter() {
    String doubled = "a,,b,c";
    Iterable<String> letters = COMMA_SPLITTER.split(doubled);
    assertThat(letters).containsExactly("a", "", "b", "c").inOrder();

     *
     * @param <T>
     *            {@link Iterable}の要素型
     * @param iterable
     *            {@link Iterable}。{@literal null}であってはいけません
     * @return {@link IndexedIterator}をラップした{@link Iterable}
     */
    public static <T> Iterable<Indexed<T>> indexed(final Iterable<T> iterable) {
        assertArgumentNotNull("iterable", iterable);