@Override
    Multiset<E> multiset() {
      return AbstractMultiset.this;
    }

    @Override
    public Iterator<E> iterator() {
      return elementIterator();
    }
  }

  abstract Iterator<E> elementIterator();

  @LazyInit private transient @Nullable Set<Entry<E>> entrySet;

  @Override
  public Set<Entry<E>> entrySet() {

まず、1 つ以上のコールバックを含む新しい `APIRouter` を作成します。

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[1,23] *}

### コールバックの path operation を作成 { #create-the-callback-path-operation }

上で作成したのと同じ `APIRouter` を使って、コールバックの *path operation* を作成します。

見た目は通常の FastAPI の *path operation* と同じです:

* 受け取るボディの宣言（例: `body: InvoiceEvent`）が必要でしょう。
* 返すレスポンスの宣言（例: `response_model=InvoiceEventReceived`）も持てます。

      SortedSet<@Nullable Object> self = (SortedSet<@Nullable Object>) this;
      Iterator<?> iterator = self.tailSet(object).iterator();
      if (iterator.hasNext()) {
        Object ceiling = iterator.next();
        if (unsafeCompare(comparator(), ceiling, object) == 0) {
          iterator.remove();
          return true;
        }
      }
    } catch (ClassCastException | NullPointerException e) {

    assertEquals(rangeSet.asDescendingSetOfRanges().isEmpty(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asRanges().iterator().hasNext(), rangeSet.isEmpty());
    assertEquals(!rangeSet.asDescendingSetOfRanges().iterator().hasNext(), rangeSet.isEmpty());

    List<Range<C>> asRanges = ImmutableList.copyOf(rangeSet.asRanges());

    // test that connected ranges are coalesced

   */
  public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
    Iterator<E> iterator = elements.iterator();
    checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
    EnumMultiset<E> multiset = new EnumMultiset<>(iterator.next().getDeclaringClass());
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  /**

    this.elementOrder = elementOrder;
  }

  @Override
  public int compare(Iterable<T> leftIterable, Iterable<T> rightIterable) {
    Iterator<T> left = leftIterable.iterator();
    Iterator<T> right = rightIterable.iterator();
    while (left.hasNext()) {
      if (!right.hasNext()) {
        return LEFT_IS_GREATER; // because it's longer
      }

    this.elementOrder = elementOrder;
  }

  @Override
  public int compare(Iterable<T> leftIterable, Iterable<T> rightIterable) {
    Iterator<T> left = leftIterable.iterator();
    Iterator<T> right = rightIterable.iterator();
    while (left.hasNext()) {
      if (!right.hasNext()) {
        return LEFT_IS_GREATER; // because it's longer
      }

import com.google.common.collect.TestExceptions.SomeUncheckedException;
import com.google.common.testing.GcFinalization;
import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.NoSuchElementException;
import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Unit test for {@code AbstractIterator}.
 *

import com.google.common.collect.TestExceptions.SomeUncheckedException;
import com.google.common.testing.GcFinalization;
import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.NoSuchElementException;
import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Unit test for {@code AbstractIterator}.
 *

      }
      return false;
    }

    @Override
    public void clear() {
      AbstractTable.this.clear();
    }

    @Override
    public Iterator<Table.Cell<R, C, V>> iterator() {
      return cellIterator();
    }

    @Override
    public Spliterator<Cell<R, C, V>> spliterator() {
      return cellSpliterator();
    }

    @Override