code: public function getDb()
      {
          if (is_null($this->_db)) {
              if (!isset($this->dbConfig['class'])) {
                  $this->dbConfig['class'] = 'cascade\components\dataInterface\connectors\db\Connection';
              }
              $this->_db = Yii::createObject($this->dbConfig);
              $this->_db->open();
          }
          if (empty($this->_db) || !$this->_db->isActive) {
              throw new Exception("Unable to connect to foreign database.");
          }
  
          return $this->_db;
      }
docs: Get db.
  
  @throws Exception on database connection failure
  @return Connection the database connection