theming – How do I make theme suggestions for pagers?

I am trying to create theme suggestions function for pagers in my *.theme. Is this possible in Drupal 8? If it is possible, what is wrong with the following code? Is suggestions_pager_alter the right way to access the hook call so I can add a theme suggestion to a page, so I can override the template. I am not worried about the functions logic.

function mytheme_suggestions_pager_alter(array &$suggestions, array $variables) {
  // Add template suggestions based on the current view mode.
   print_r(); exit;