public function getPurchaseInvoiceLines($statement = '')
    {
        if (array_key_exists('__deferred', $this->attributes['PurchaseInvoiceLines'])) {
            $this->attributes['PurchaseInvoiceLines'] = (new PurchaseInvoiceLine($this->connection()))->filter("InvoiceID eq guid'{$this->ID}'", '', '', $statement);
        }

        return $this->attributes['PurchaseInvoiceLines'];
    }