public function splitItems($items)
    {
        $data = array(
            'items' => array_map(function(ItemSplit $item) {
                return $item->serialize();
            }, $items)
        );

        $data = $this->twisto->requestJson('POST', 'invoice/' . urlencode($this->invoice_id) . '/split/', $data);
        $split_invoice = new Invoice($this->twisto, null);
        $split_invoice->deserialize($data);
        $this->get();

        return $split_invoice;
    }