Get a scope of a relationship laravel

I can not access to $ad->stats->todayImpressions(); in my detail view of an ads. How can access to a filter relationship? When I try to dump this:

dd($ad->stats->todayImpressions());

I get this error:

Method todayImpressions does not exist.

These are the two model involved:

class Ad extends Model
{
   /**
    * The stats that belong to the ads.
    */
    public function stats(){
     return $this->hasMany('App\Models\Stats', 'ad', 'id');
    }
}

class Stats extends Model
{
   /**
   * The # of the today impressions for the current stats.
   */
   public function scopeTodayImpressions($query) {
    $todayTime = strtotime('today midnight');
    return $query->where('thetime', $todayTime);
 }
}

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