private static boolean hasPermittedSubclassModifier(@NotNull PsiClass psiClass) {
    PsiModifierList modifiers = psiClass.getModifierList();
    if (modifiers == null) return false;
    return modifiers.hasModifierProperty(PsiModifier.SEALED) ||
           modifiers.hasModifierProperty(PsiModifier.NON_SEALED) ||
           modifiers.hasModifierProperty(PsiModifier.FINAL);
  }
private static boolean hasPermittedSubclassModifier(@NotNull PsiClass psiClass)