code: def exists(self, client=None, retry=DEFAULT_RETRY):
          
          client = self._require_client(client)
  
          extra_params = {"fields": "id"}
          if self.location:
              extra_params["location"] = self.location
  
          try:
              client._call_api(
                  retry, method="GET", path=self.path, query_params=extra_params
              )
          except NotFound:
              return False
          else:
              return True
docs: API call:  test for the existence of the job via a GET request
  
          See
          https://cloud.google.com/bigquery/docs/reference/rest/v2/jobs/get
  
          :type client: :class:`~google.cloud.bigquery.client.Client` or
                        ``NoneType``
          :param client: the client to use.  If not passed, falls back to the
                         ``client`` stored on the current dataset.
  
          :type retry: :class:`google.api_core.retry.Retry`
          :param retry: (Optional) How to retry the RPC.
  
          :rtype: bool
          :returns: Boolean indicating existence of the job.