Ouzo\Utilities\Functions::call PHP Method

    public static function call($function, $argument)
    {
        return call_user_func($function, $argument);
    }

 private function _map($closure)
 {
     if ($this->isPresent()) {
         return Optional::fromNullable(Functions::call($closure, $this->object));
     }
     return Optional::absent();
 }