pager_serializer-8.x-1.0/tests/modules/rest_test_views/pager_serializer_test_views.module

<?php

/**
 * @file
 * Test hook implementations for the REST views test module.
 */

use Drupal\views\ViewExecutable;

/**
 * Implements hook_views_post_execute().
 */
function pager_serializer_test_views_views_post_execute(ViewExecutable $view) {
  // Attach a custom header to the test_data_export view.
  if ($view->id() === 'test_serializer_display_entity') {
    if ($value = \Drupal::state()->get('pager_serializer_test_views_set_header', FALSE)) {
      $view->getResponse()->headers->set('Custom-Header', $value);
    }
  }

}