code: def _get_bigquery_service(self):
          
          logger.debug('Getting Google Credentials')
          credentials = GoogleCredentials.get_application_default()
          logger.debug('Building BigQuery service instance')
          bigquery_service = build('bigquery', 'v2', credentials=credentials)
          return bigquery_service
docs: Connect to the BigQuery service.
  
          Calling ``GoogleCredentials.get_application_default`` requires that
          you either be running in the Google Cloud, or have the
          ``GOOGLE_APPLICATION_CREDENTIALS`` environment variable set to the path
          to a credentials JSON file.
  
          :return: authenticated BigQuery service connection object
          :rtype: `googleapiclient.discovery.Resource <http://google.github.io/\
  google-api-python-client/docs/epy/googleapiclient.discovery.\
  Resource-class.html>`_