def METHOD_NAME(self):
    """Test corner case where a network might predict no boxes and no
    gt."""
    atss_assigner = ATSSAssigner(topk=9)
    priors = torch.empty((0, 4))
    gt_bboxes = torch.empty((0, 4))
    gt_labels = torch.empty(0)
    num_level_bboxes = [0]
    pred_instances = InstanceData(priors=priors)
    gt_instances = InstanceData(bboxes=gt_bboxes, labels=gt_labels)
    assign_result = atss_assigner.assign(pred_instances, num_level_bboxes,
                                         gt_instances)
    self.assertEqual(len(assign_result.gt_inds), 0)