A client that uses the faster BigQuery Storage API to fetch rows from BigQuery. If not passed, it is created using the same credentials as client (provided that BigQuery Storage dependencies are installed). If both clients are available, bqstorage_client is used for fetching query results.
Close the connection and any cursors created from it.
Any BigQuery clients explicitly passed to the constructor are not
closed, only those created by the connection instance itself.
No-op, but for consistency raise an error if connection is closed.