/**
  * @param \Illuminate\Database\Eloquent\Model $model
  * @param string $event
  * @return boolean|null
  */
 protected function generateSlug(Model $model, $event)
 {
     // If the "slugging" event returns a value, abort
     if ($this->fireSluggingEvent($model, $event) !== null) {
         return;
     }
     $wasSlugged = $this->slugService->slug($model);
     $this->fireSluggedEvent($model, $wasSlugged);
 }