Training with a custom service account needs a new field named service account
trainingInput:
  serviceAccount: CUSTOM_SERVICE_ACCOUNT

https://cloud.google.com/ai-platform/training/docs/custom-service-account


tests/providers/google/cloud/operators/test_mlengine.py
http_error_code = 403
        hook_instance = mock_hook.return_value
        hook_instance.cancel_job.side_effect = HttpError(
            resp=httplib2.Response({'status': http_error_code}), content=b'Forbidden'
        )
        with self.assertRaises(HttpError) as context:
            cancel_training_op = MLEngineTrainingCancelJobOperator(**self.TRAINING_DEFAULT_ARGS)
            cancel_training_op.execute(None)
        mock_hook.assert_called_once_with(
            gcp_conn_id='google_cloud_default',
            delegate_to=None,
            impersonation_chain=None,
        )
        
        self.assertEqual(len(hook_instance.mock_calls), 1)
        hook_instance.cancel_job.assert_called_once_with(
            project_id=self.TRAINING_DEFAULT_ARGS['project_id'], job_id=self.TRAINING_DEFAULT_ARGS['job_id']
        )
        self.assertEqual(http_error_code, context.exception.resp.status)
class TestMLEngineModelOperator(unittest.TestCase):