public function processUploadElement(array $element, FormStateInterface $form_state) {
    $element = AjaxUpload::process($element, $form_state);

    $element['upload']['#ajax']['callback'] =
    $element['remove']['#ajax']['callback'] = [static::class, 'ajax'];

    $element['remove']['#value'] = $this->t('Cancel');

    return $element;
  }