def __exit__()

in upload.py [0:0]


    def __exit__(self, exc_type, exc_value, traceback):
        """Abort the opened session."""
        if self._session_cfg:
            # abort the session in any case to have a clean state at the end
            # (sometimes in case of script failure, the table is locked in
            # the session)
            job = self._bigquery_client.query(
                "CALL BQ.ABORT_SESSION();",
                job_config=self._session_cfg.config(bigquery.QueryJobConfig())
            )
            job.result()