private function normalizeFeatures(array $features)
    {
        $result = [];

        foreach ($features as $key => $feature) {
            $maxResults = $this->maxResult($feature);

            if (array_key_exists($feature, $this->featureShortNames)) {
                $feature = $this->featureShortNames[$feature];
            }

            $result[] = array_filter([
                'type' => $feature,
                'maxResults' => $maxResults
            ]);
        }

        return $result;
    }