public function set_help()
 {
     if (self::$last_help) {
         $help_to_add = self::$last_help;
         self::$last_help = '';
     } else {
         $descriptions = pakePHPDoc::getDescriptions($this->getCallable());
         $help_to_add = $descriptions[1];
     }
     if (empty($help_to_add)) {
         return;
     }
     $this->help = $help_to_add;
 }