public function send()
    {
        $aReminder = $this->json();
        $aReminder = json_decode($aReminder, true);

        $aReminder['sales_invoice_ids'] = array_map(function ($salesInvoice) {
            if (is_object($salesInvoice)) {
                return $salesInvoice->id;
            } else {
                return $salesInvoice;
            }
        }, $this->sales_invoices);
        unset($aReminder['sales_invoices']);

        $this->connection->post($this->endpoint . '/send_reminders', json_encode([
            'sales_invoice_reminders' => [$aReminder],
        ]));
    }