Initiate a bulk insert and upload batches to run in parallel.

def _create_job(self, mapping):
        """Initiate a bulk insert and upload batches to run in parallel."""
        job_id = self.bulk.create_insert_job(mapping["sf_object"], contentType="CSV")
        self.logger.info("  Created bulk job {}".format(job_id))

        # Upload batches
        local_ids_for_batch = {}
        for batch_file, local_ids in self._get_batches(mapping):
            batch_id = self.bulk.post_batch(job_id, batch_file)
            local_ids_for_batch[batch_id] = local_ids
            self.logger.info("    Uploaded batch {}".format(batch_id))

        self.bulk.close_job(job_id)
        return job_id, local_ids_for_batch