def METHOD_NAME(dataloader: torch.utils.data.DataLoader) -> None:
    dataset = dataloader.dataset
    sampler = mh_mmdet.GroupSampler(dataset, 2, 1)
    flags = [dataset.flag[i] for i in sampler]  # type: ignore
    test = [flags[i] == flags[i + 1] for i in range(0, len(flags), 2)]
    assert all(test)