class Item:
    name: str
    price: float
    tags: List[str] = field(default_factory=list)
    description: Union[str, None] = None
    tax: Union[float, None] = None


app = FastAPI()


@app.get("/items/next", response_model=Item)
async def read_next_item():
    return {
        "name": "Island In The Moon",
        "price": 12.99,
        "description": "A place to be playin' and havin' fun",
        "tags": ["breater"],

      @CheckForNull
      protected C computeNext() {
        while (merged.hasNext()) {
          C next = merged.next();
          boolean duplicate = lastValue != null && comparator.compare(next, lastValue) == 0;

          // Keep looping till we find a non-duplicate value.
          if (!duplicate) {
            lastValue = next;
            return lastValue;
          }
        }

      String nextSeparator = "";
      StringBuilder builder = new StringBuilder(32).append(className).append('{');
      for (ValueHolder valueHolder = holderHead.next;
          valueHolder != null;
          valueHolder = valueHolder.next) {
        Object value = valueHolder.value;
        if (valueHolder instanceof UnconditionalValueHolder
            || (value == null
                ? !omitNullValuesSnapshot

    Entry<String, Integer> entry = entries.next();
    assertEquals("bar", entry.getKey());
    assertEquals(1, (int) entry.getValue());
    entry = entries.next();
    assertEquals("foo", entry.getKey());
    assertEquals(2, (int) entry.getValue());
    entry.setValue(4);
    entry = entries.next();
    assertEquals("bar", entry.getKey());
    assertEquals(3, (int) entry.getValue());

 *       next task will wait for any running callable (or pending {@code Future} returned by an
 *       {@code AsyncCallable}) to complete, without interrupting it (and without calling {@code
 *       cancel} on the {@code Future}). So beware: <i>Even if you cancel every preceding {@code
 *       Future} returned by this class, the next task may still have to wait.</i>.

  @Override
  public final boolean hasNext() {
    return backingIterator.hasNext();
  }

  @Override
  @ParametricNullness
  public final T next() {
    return transform(backingIterator.next());
  }

  @Override
  public final void remove() {
    backingIterator.remove();
  }

But first, let's check some small concepts.

## In a hurry?

If you don't care about any of these terms and you just need to add security with authentication based on username and password *right now*, skip to the next chapters.

## OAuth2

OAuth2 is a specification that defines several ways to handle authentication and authorization.

It is quite an extensive specification and covers several complex use cases.

    }.test();
  }

  public void testIteratorNoSuchElementException() {
    Iterator<E> iterator = collection.iterator();
    while (iterator.hasNext()) {
      iterator.next();
    }

    assertThrows(NoSuchElementException.class, () -> iterator.next());
  }

    assertEquals(ImmutableSet.of(), i.next());
    assertEquals(ImmutableSet.of(1), i.next());
    assertEquals(ImmutableSet.of(2), i.next());
    assertEquals(ImmutableSet.of(2, 1), i.next());
    assertEquals(ImmutableSet.of(3), i.next());
    assertEquals(ImmutableSet.of(3, 1), i.next());
    assertEquals(ImmutableSet.of(3, 2), i.next());
    assertEquals(ImmutableSet.of(3, 2, 1), i.next());
    assertFalse(i.hasNext());

	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}
	r.err = err
	return r.current, err
}

// next will read one entry from the stream.
// Generally not recommended for fast operation.
func (r *metacacheReader) next() (metaCacheEntry, error) {
	r.checkInit()
	if r.err != nil {
		return metaCacheEntry{}, r.err
	}
	var m metaCacheEntry
	var err error