/**
 * Implements hook_node_access_records_alter().
 */
function {{ machine_name }}_node_access_records_alter(&$grants, Drupal\node\NodeInterface $node) {
  // Our module allows editors to mark specific articles with the 'is_preview'
  // field. If the node being saved has a TRUE value for that field, then only
  // our grants are retained, and other grants are removed. Doing so ensures
  // that our rules are enforced no matter what priority other grants are given.
  if ($node->is_preview) {
    // Our module grants are set in $grants['example'].
    $temp = $grants['example'];
    // Now remove all module grants but our own.
    $grants = ['example' => $temp];
  }
}