/**
  * Get a paginator for a grouped statement.
  *
  * @param  \Pagination\Factory  $paginator
  * @param  int    $perPage
  * @param  array  $columns
  * @return \Pagination\Paginator
  */
 protected function groupedPaginate($paginator, $perPage, $columns)
 {
     $results = $this->get($columns)->all();
     return $this->query->buildRawPaginator($paginator, $results, $perPage);
 }