def METHOD_NAME(self):
    transforms = T.TransformList([T.HFlipTransform(400)])
    mask = np.zeros((300, 400), order="F").astype("uint8")
    mask[:, :200] = 1
    anno = {
        "bbox": np.asarray([10, 10, 200, 300]),
        "bbox_mode": BoxMode.XYXY_ABS,
        "segmentation": mask_util.encode(mask[:, :, None])[0],
        "category_id": 3,
    }
    output = detection_utils.transform_instance_annotations(
        copy.deepcopy(anno), transforms, (300, 400)
    )
    mask = output["segmentation"]
    self.assertTrue((mask[:, 200:] == 1).all())
    self.assertTrue((mask[:, :200] == 0).all())
    inst = detection_utils.annotations_to_instances(
        [output, output], (400, 400), mask_format="bitmask"
    )
    self.assertTrue(isinstance(inst.gt_masks, BitMasks))