drupalcampbristol/vendor/chi-teck/drupal-code-generator/templates/d8/hook/rebuild.twig

/**
 * Implements hook_rebuild().
 */
function {{ machine_name }}_rebuild() {
  $themes = \Drupal::service('theme_handler')->listInfo();
  foreach ($themes as $theme) {
    _block_rehash($theme->getName());
  }
}