* A {@link Scheduler} that provides a convenient way for the {@link AbstractScheduledService} to
   * use a dynamically changing schedule. After every execution of the task, assuming it hasn't been
   * cancelled, the {@link #getNextSchedule} method will be called.
   *
   * @author Luke Sandberg
   * @since 11.0
   */
  public abstract static class CustomScheduler extends Scheduler {