code: public function findPrimaryKeys($params = [])
      {
          $q = $this->find($params);
          $q->select($this->_tableName . '.' . $this->meta->schema->primaryKey[0]);
  
          return $q->column($this->interface->db);
      }
docs: Return the primary keys (used in lazy loading).
  
  @param array $params find params for the query [optional]
  
  @return array keys from the data source items