function last(callable $closure = null) {
        if($closure === null) {
            if(empty($this->data)) {
                return null;
            }
            
            $keys = \array_keys($this->data);
            return $this->data[$keys[(\count($keys) - 1)]];
        }
        
        $data = null;
        foreach($this->data as $key => $val) {
            $feed = $closure($val, $key);
            if($feed) {
                $data = $val;
            }
        }
        
        return $data;
    }