mailjet-8.x-2.7/modules/mailjet_subscription/mailjet_subscription.module

<?php

use \Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Drupal\mailjet_subscription\Entity\SubscriptionForm;

/**
 * @file
 * Define Mailjet Signup Conifuration type.
 */

/**
 * Implements hook_form_alter().
 */
function mailjet_subscription_form_alter(&$form, FormStateInterface $form_state) {
  $form_id = $form['#form_id'];
  if ($form_id == 'mailjet_subscription_form_edit_form') {
    $form['actions']['edit_labels'] = [
      '#type' => 'submit',
      '#weight' => 3,
      '#limit_validation_errors' => [],
      '#button_type' => 'primary',
      '#submit' => [
        'mailjet_subscription_redicrect_to_edit_form',
      ],
      '#value' => t('Edit Labels'),
    ];
    $form['#attached']['library'][] = 'mailjet_subscription/sort_properties';
  }
}

function mailjet_subscription_redicrect_to_edit_form(&$form, FormStateInterface $form_state) {
  $entity_id = $form['id']['#default_value'];

  global $base_url;

  $response = new RedirectResponse($base_url . '/admin/config/system/mailjet/signup-settings/labels?entity-id=' . $entity_id);
  $response->send();
}

/**
 * Loads a single Subscription entity by ID.
 *
 * @param int $subscription_id
 *   The ID of the Subscription entity entity to load.
 *
 */
function mailjet_subscription_load($signup_id) {
  return SubscriptionForm::load($signup_id);
}

/**
 * Loads multiple Subscription entity forms entities.
 *
 */
function mailjet_subscription_load_multiple($signup_ids = [], $reset = FALSE) {
  if (empty($signup_ids)) {
    $signup_ids = NULL;
  }

  $controller = \Drupal::entityTypeManager()
    ->getStorage('mailjet_subscription_form');

  if ($reset) {
    $controller->resetCache($signup_ids);
  }

  return $controller->loadMultiple($signup_ids);
}