private function getMetrics()
    {
        $metrics = [
            $this->metricFactory->create(
                ['name' => 'unique_sessions', 'field' => 'session.uid', 'type' => MetricInterface::TYPE_CARDINALITY]
            ),
            $this->metricFactory->create(
                ['name' => 'unique_visitors', 'field' => 'session.vid', 'type' => MetricInterface::TYPE_CARDINALITY]
            ),
            $this->metricFactory->create(
                ['name' => 'spellcheck_usage', 'field' => 'page.search.is_spellchecked', 'type' => MetricInterface::TYPE_STATS]
            ),
        ];

        return $metrics;
    }