How to use groupBy on query based on the search API views?

My search api query returns a list of articles with its nid and field category. I would like to group by category. I mean 1 article by category. Is there a way to accomplish this? I tried via the _views_query_alter but it looks that SearchApiQuery $query has not the function groupBy.

Ex:

HOOK_views_query_alter(\Drupal\views\ViewExecutable $view, \Drupal\views\Plugin\views\query\QueryPluginBase $query) {

     /** @var \Drupal\search_api\Plugin\views\query\SearchApiQuery $query */
     $query->addCondition('search_api_language', \Drupal::languageManager()->getCurrentLanguage()->getId());
     $query->groupBy('field_category');// NOT DEFINED
}

Not grouped:

 `{
   'nid': 1, 'field_category' :34,
   'nid': 2, 'field_category' :34,
   'nid': 3, 'field_category' :35
 }`

Grouped:

{
   'nid': 1, 'field_category' :34,
   'nid': 3, 'field_category' :35
 }