}
    },
    ;

    abstract <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario);
  }

  /**
   * A dummy object we create so that we can have something meaningful to have a compound ordering
   * over.
   */
  private static class Composite<T extends @Nullable Object> implements Comparable<Composite<T>> {
    final T value;
    final int rank;

      }
    },
    ;

    abstract <T extends @Nullable Object> Scenario<?> mutate(Scenario<T> scenario);
  }

  /**
   * A dummy object we create so that we can have something meaningful to have a compound ordering
   * over.
   */
  private static class Composite<T extends @Nullable Object> implements Comparable<Composite<T>> {
    final T value;
    final int rank;