public function get_po_files($id_option){
    if (!empty($id_option) && ($o = options::get_instance()->option($id_option)) &&
    ($parent = options::get_instance()->parent($id_option)) &&
    defined($parent['code']) ){
      $tmp = [];
      // @var  $to_explore the path to explore 
      $to_explore = constant($parent['code']).$o['code'];
      // @var  $locale_dir locale dir in the path
      $locale_dir = dirname($to_explore).'/locale';
      $dirs = \bbn\file\dir::get_dirs($locale_dir) ?: [];
      $languages = array_map(function($a){
        return basename($a);
      }, $dirs) ?: [];
      if ( !empty($languages) ){

        foreach ( $languages as $lng ){
          // the path of po and mo files 
          $idx = is_file($locale_dir.'/index.txt') ? file_get_contents($locale_dir.'/index.txt') : '';
          if ( is_file($locale_dir.'/'.$lng.'/LC_MESSAGES/'.$o['text'].$idx.'.po') ){
            $tmp[$lng]= $locale_dir.'/'.$lng.'/LC_MESSAGES/'.$o['text'].$idx.'.po';
          }

        }

      }

      return $tmp;
    }
  }