$builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
               //$Customer = $event->getData();
                //if ($Customer instanceof Customer && !$Customer->getId()) {
                    $form = $event->getForm();
    
                    $form->add('user_policy_check', CheckboxType::class, [
                            'required' => true,
                            'label' => null,
                            'mapped' => false,
                            'constraints' => [
                                new Assert\NotBlank(),
                            ],
                        ]);
                //}
            }
 );