HierarchyFixtureInterface.class,
            HierarchyFixtureSubinterface.class,
            HierarchyFixtureParent.class,
            HierarchyFixture.class),
        SubscriberRegistry.flattenHierarchy(HierarchyFixture.class));
  }

  private interface HierarchyFixtureInterface {
    // Exists only for hierarchy mapping; no members.
  }