public function listExtensions($type)
    {
        $results = [];

        if ($this->items === null) {
            $this->loadExtensions();
        }

        if (isset($this->items[$type]) && is_array($this->items[$type])) {
            $results = $this->items[$type];
        }

        if ($this->transactionItems !== null && isset($this->transactionItems[$type])) {
            $results = array_merge($results, $this->transactionItems[$type]);
        }

        return $results;
    }