private function listEntityIdsWithoutCps(PagerInterface $pager = null, array $query_params = []): array
    {
        $query_params = [
                'expand' => 'false',
            ] + $query_params;

        $uri = $this->getBaseEndpointUri()->withQuery(http_build_query($query_params));
        $response = $this->getClient()->get($uri);

        $ids = $this->responseToArray($response);

        // Re-key the array from 0 if CPS had to be simulated.
        return $pager ? array_values($this->simulateCpsPagination($pager, $ids)) : $ids;
    }