private static @Nullable LanguageLevel parseLanguageLevel(@NotNull String languageLevelString, boolean isPreview) {
    LanguageLevel languageLevel = LanguageLevel.parse(languageLevelString);
    if (languageLevel == null) return null;
    return setPreview(languageLevel, isPreview);
  }
private static @Nullable LanguageLevel parseLanguageLevel(@NotNull String languageLevelString, boolean isPreview)