def METHOD_NAME(self, request, queryset):
    if queryset.count() > 1:
        self.message_user(request, "Please select only one Page to set as locked custom switch page for all Signs.", level="ERROR")
        return
    page = queryset.first()
    for sign in Sign.objects.all():
        sign.pages.add(page)
        sign.custom_switch_page = page
        sign.custom_switch_page_lock = True
        sign.save()
    self.message_user(
        request, f"Successfully set {page.name} as locked custom switch page for all Signs. Set a custom switch time to activate this page."
    )