I am trying to add a CSS file to the front page. I have seen [Adding stylesheets (CSS) and JavaScript (JS) to a Drupal 8 theme][1]; I just need to know the HOOK machine name for the front page.

 function THEMENAME_preprocess_HOOK(&$variables) {
 $variables['#attached']['library'][] = 'CSSPATH';
 }


What name should I use for the preprocess function, in order to make Drupal calls it only for the front page?












 [1]: https://www.drupal.org/theme-guide/8/assets