code: @CheckResult @NonNull
    public <T extends Enum<T>> Preference<T> getEnum(@NonNull String key, @NonNull T defaultValue,
        @NonNull Class<T> enumClass) {
      checkNotNull(key, "key == null");
      checkNotNull(defaultValue, "defaultValue == null");
      checkNotNull(enumClass, "enumClass == null");
      return new RealPreference<>(preferences, key, defaultValue, new EnumAdapter<>(enumClass), keyChanges);
    }
docs: Create an enum preference for {@code key} with a default of {@code defaultValue}.