/**
   * Precondition tester for {@code Iterator.remove()} that throws an exception with a consistent
   * error message.
   */
  static void checkRemove(boolean canRemove) {
    checkState(canRemove, "no calls to next() since the last call to remove()");
  }

  private CollectPreconditions() {}

    private final ReferenceEntry<K, V> next;

    public DummyEntry(K key, int hash, ReferenceEntry<K, V> next) {
      this.key = key;
      this.hash = hash;
      this.next = next;
    }

    public static <K, V> DummyEntry<K, V> create(
        K key, int hash, @Nullable ReferenceEntry<K, V> next) {
      return new DummyEntry<>(key, hash, next);
    }

    public void clearKey() {

    private final ReferenceEntry<K, V> next;

    public DummyEntry(K key, int hash, ReferenceEntry<K, V> next) {
      this.key = key;
      this.hash = hash;
      this.next = next;
    }

    public static <K, V> DummyEntry<K, V> create(
        K key, int hash, @Nullable ReferenceEntry<K, V> next) {
      return new DummyEntry<>(key, hash, next);
    }

    public void clearKey() {

1. Click **Management**.
1. Click **Index Patterns**.
1. Click **Create index pattern** button
1. Input "fess\_log\*" to the textbox of **index pattern**.
1. Click **Next step**.
1. Set "requestedAt" to the **Time Filter field name**.
1. Click **Create index pattern**.
1. Click **Saved Objects**.
1. Click **Import** and select "fess\_log.ndjson" to import example settings.

The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.

## Documenting the callback { #documenting-the-callback }

The actual callback code will depend heavily on your own API app.

And it will probably vary a lot from one app to the next.

It could be just one or two lines of code, like:

```Python
callback_url = "https://example.com/api/v1/invoices/events/"

	// A character used to truncate the object prefixes.
	// NOTE: only supported delimiter is '/'.
	Delimiter string

	// CommonPrefixes contains all (if there are any) keys between Prefix and the
	// next occurrence of the string specified by delimiter.
	CommonPrefixes []string

	EncodingType string // Not supported yet.
}

// TransitionedObject transitioned object tier and status.

  }

  private static final class MyIntegerDomain extends DiscreteDomain<Integer> {
    static final DiscreteDomain<Integer> DELEGATE = DiscreteDomain.integers();

    @Override
    public Integer next(Integer value) {
      return DELEGATE.next(value);
    }

    @Override
    public Integer previous(Integer value) {
      return DELEGATE.previous(value);
    }

        continue
      }

      // Search for the certificate in the chain that signed this certificate. This is typically
      // the next element in the chain, but it could be any element.
      val i = queue.iterator()
      while (i.hasNext()) {
        val signingCert = i.next() as X509Certificate
        if (verifySignature(toVerify, signingCert, result.size - 1)) {
          i.remove()
          result.add(signingCert)

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

      @Override
      public V next() {
        return entryItr.next().getValue();
      }
    };
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && Iterators.contains(iterator(), object);
  }

  @Override

@NullUnmarked
public class ContiguousSetTest extends TestCase {
  private static final DiscreteDomain<Integer> NOT_EQUAL_TO_INTEGERS =
      new DiscreteDomain<Integer>() {
        @Override
        public Integer next(Integer value) {
          return integers().next(value);
        }

        @Override
        public Integer previous(Integer value) {
          return integers().previous(value);
        }

        @Override