throw new AssertionError("should never be called");
    }

    @Override
    Set<Entry<E>> createEntrySet() {
      return Sets.filter(unfiltered.entrySet(), entry -> predicate.apply(entry.getElement()));
    }

    @Override
    Iterator<Entry<E>> entryIterator() {
      throw new AssertionError("should never be called");
    }

    @Override

      throw new AssertionError("should never be called");
    }

    @Override
    Set<Entry<E>> createEntrySet() {
      return Sets.filter(unfiltered.entrySet(), entry -> predicate.apply(entry.getElement()));
    }

    @Override
    Iterator<Entry<E>> entryIterator() {
      throw new AssertionError("should never be called");
    }

    @Override

    return eventBus;
  }

  /** Returns the event object that caused the subscriber to throw. */
  public Object getEvent() {
    return event;
  }

  /** Returns the object context that the subscriber was called on. */
  public Object getSubscriber() {
    return subscriber;
  }

  /** Returns the subscribed method that threw the exception. */
  public Method getSubscriberMethod() {
    return subscriberMethod;
  }

    return new AnEnum[length];
  }

  /** Sorts the enums according to their natural ordering. */
  /*
   * While the current implementation returns `this`, that's not something we mean to guarantee.
   * Callers of TestContainerGenerator.order need to be prepared for implementations to return a new
   * collection.
   */
  @SuppressWarnings("CanIgnoreReturnValueSuggester")
  @Override

  /** Sorts the elements by their natural ordering. */
  /*
   * While the current implementation returns `this`, that's not something we mean to guarantee.
   * Callers of TestContainerGenerator.order need to be prepared for implementations to return a new
   * collection.
   */
  @SuppressWarnings("CanIgnoreReturnValueSuggester")
  @Override

   * {@code x}. This must not be called on a vertical transformation (i.e. when {@link
   * #isVertical()} is true).
   */
  public abstract double slope();

  /**
   * Returns the {@code y} corresponding to the given {@code x}. This must not be called on a
   * vertical transformation (i.e. when {@link #isVertical()} is true).
   */

 * family. <b>Avoid</b> creating a mock or stub {@code Future}. Mock and stub implementations are
 * fragile because they assume that only certain methods will be called and because they often
 * implement subtleties of the API improperly.
 *
 * <p><b>Custom implementation</b>: Avoid implementing {@code ListenableFuture} from scratch. If you

   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection
   * @param sampleElement an element of the same type as that contained by {@code collection}.

     */
    final Stack<E> previousElements = new Stack<>();

    /**
     * {@link #nextElements} if {@code next()} was called more recently then {@code previous},
     * {@link #previousElements} if the reverse is true, or -- overriding both of these -- {@code
     * null} if {@code remove()} or {@code add()} has been called more recently than either. We use
     * this to determine which stack to pop from on a call to {@code remove()} (or to pop from and

     */
    boolean available();

    /**
     * Cleans up resources and performs any necessary finalization tasks
     * before the object is destroyed. This method should be called to
     * ensure that all resources are properly released.
     */
    void destroy();

    /**
     * Initializes the CrawlerContainer by setting the system property