static @NotNull MultiMap<LanguageLevel, Module> getUnacceptedLevels(@NotNull Project project, TreeSet<LanguageLevel> previewLevels) {
    MultiMap<LanguageLevel, Module> unacceptedLevels = new MultiMap<>();
    LanguageLevelProjectExtension projectExtension = LanguageLevelProjectExtension.getInstance(project);
    if (projectExtension != null) {
      LanguageLevel level = projectExtension.getLanguageLevel();
      if (!isLanguageLevelAccepted(level)) {
        unacceptedLevels.putValue(level, null);
      }
      if (level.isPreview()) {
        previewLevels.add(level);
      }
    }
    for (Module module : ModuleManager.getInstance(project).getModules()) {
      LanguageLevel level = LanguageLevelUtil.getCustomLanguageLevel(module);
      if (level != null) {
        if (!isLanguageLevelAccepted(level)) {
          unacceptedLevels.putValue(level, module);
        }
        if (level.isPreview()) {
          previewLevels.add(level);
        }
      }
    }
    return unacceptedLevels;
  }
static @NotNull MultiMap<LanguageLevel, Module> getUnacceptedLevels(@NotNull Project project, TreeSet<LanguageLevel> previewLevels)