code: protected function expand()
      {
          foreach ($this as $key => $item) {
              $item['slug'] = $key;
  
              if (isset($item['date'])) {
                  $item['formatted_date'] = date(self::DATE_FORMAT, $item['date']);
              }
  
              $this->set($key, $item);
          }
      }
docs: Expands each collection item with extra data