mailjet-8.x-2.7/modules/mailjet_campaign/src/Controller/CampaignUninstallController.php

<?php

/**
 * @file
 * Contains \Drupal\mailjet_campaign\Controller\CampaignUninstallController.
 */

namespace Drupal\mailjet_campaign\Controller;

use Drupal\Core\Controller\ControllerBase;

class CampaignUninstallController extends ControllerBase
{

    public function callback()
    {
        $build = [];

        $controller = \Drupal::entityTypeManager()->getStorage('campaign_entity');
        $entities = $controller->loadMultiple();
        $controller->delete($entities);

        \Drupal::messenger()->addMessage(t('Campaign entities is removing succcefully!'));
        return $build;
    }

}