public function getLocations() {
    $sql = "SELECT DISTINCT nd.title as location 
            FROM {node} n
            INNER JOIN node__field_session_location l ON n.nid = l.entity_id AND l.bundle = 'session'
            INNER JOIN node_field_data nd ON l.field_session_location_target_id = nd.nid
            WHERE n.type = 'session'
            ORDER BY location ASC";

    $connection = \Drupal::database();
    $query = $connection->query($sql);

    $result = $query->fetchCol();
    natsort($result);
    return $result;
  }