compareTo = 0;
    }
  }

  @FunctionalInterface
  interface Construction<T> {
    @CanIgnoreReturnValue
    T create(List<?> keys);

    static Construction<Map<Object, Object>> mapFromKeys(
        Supplier<Map<Object, Object>> mutableSupplier) {
      return keys -> {
        Map<Object, Object> map = mutableSupplier.get();
        for (Object key : keys) {
          map.put(key, new Object());