def METHOD_NAME(self):
    boxes = torch.rand((10, 4))
    class_ids = torch.randint(0, 3, (10, ))
    scores = torch.rand((10, ))
    class_names = np.array(['a', 'b', 'c'])[class_ids.numpy()]
    boxlist = BoxList(
        boxes, class_ids=class_ids, scores=scores, class_names=class_names)
    boxlist = BoxList(
        boxes,
        **boxlist._map_extras(
            func=lambda k, v: v[:-1],
            cond=lambda k, v: torch.is_tensor(v)))
    self.assertTrue(
        torch.equal(boxlist.get_field('class_ids'), class_ids[:-1]))
    self.assertTrue(torch.equal(boxlist.get_field('scores'), scores[:-1]))
    self.assertTrue(all(class_names == boxlist.get_field('class_names')))