def METHOD_NAME(
    univariate_ts, multivariate_ts, train_fill_rule
) -> None:
    univariate_ds = ListDataset(univariate_ts, freq="1D")
    multivariate_ds = ListDataset(
        multivariate_ts, freq="1D", one_dim_target=False
    )
    grouper = MultivariateGrouper(train_fill_rule=train_fill_rule)
    assert (
        list(grouper(univariate_ds))[0]["target"]
        == list(multivariate_ds)[0]["target"]
    ).all()
    assert (
        list(grouper(univariate_ds))[0]["start"]
        == list(multivariate_ds)[0]["start"]
    )