public static @Nullable LanguageLevel getCustomLanguageLevel(@NotNull Module module) {
    LanguageLevelModuleExtension moduleExtension = ModuleRootManager.getInstance(module).getModuleExtension(LanguageLevelModuleExtension.class);
    return moduleExtension != null ? moduleExtension.getLanguageLevel() : null;
  }
public static @Nullable LanguageLevel getCustomLanguageLevel(@NotNull Module module)