code: public function getTagCount($ids)
      {
          $tableName = $this->getTagSource();
          $colNameId = $this->getIdColumn();
          $return    = [];
  
          if ($tableName && $colNameId) {
              $statement = $this->getConnection()->createQueryBuilder()
                  ->select('item_id', 'count(*) as count')
                  ->from('tl_metamodel_tag_relation')
                  ->where('att_id=:att')
                  ->andWhere('item_id IN (:items)')
                  ->groupBy('item_id')
                  ->setParameter('att', $this->get('id'))
                  ->setParameter('items', $ids, Connection::PARAM_INT_ARRAY)
                  ->execute();
  
              while ($row = $statement->fetch(\PDO::FETCH_OBJ)) {
                  $itemId = $row->item_id;
  
                  $return[$itemId] = (int) $row->count;
              }
          }
  
          return $return;
      }
docs: Determine the amount of entries in the relation table for this attribute and the given value ids.
  
  @param int[] $ids The ids of the items for which the tag count shall be determined.
  
  @return int[] The counts in the array format 'item_id' => count