code: public function isMarked(string $id): bool
      {
          $count = $this->connection
              ->createQueryBuilder()
              ->select('count(marker)')
              ->from($this->table, 'marker')
              ->where('marker.id = :id')
              ->setParameter('id', $id)
              ->execute()
              ->fetchColumn();
  
          return $count > 0;
      }
docs: {@inheritdoc}