/**
 * Implements hook_node_grants().
 */
function {{ machine_name }}_node_grants(\Drupal\Core\Session\AccountInterface $account, $op) {
  if ($account->hasPermission('access private content')) {
    $grants['example'] = [1];
  }
  if ($account->id()) {
    $grants['example_author'] = [$account->id()];
  }
  return $grants;
}