def METHOD_NAME():
    region_no = Region.from_fips("22071")  # Orleans Parish
    metrics_unmodified_regions = {
        # State of Louisiana, used to estimate region_no vaccinations
        Region.from_state("LA"): {
            CommonFields.VACCINATIONS_COMPLETED: [100, 200],
            CommonFields.VACCINATIONS_INITIATED: [50, 150],
        },
    }
    ds_in = test_helpers.build_dataset(
        {**metrics_unmodified_regions, region_no: {CommonFields.VACCINATIONS_COMPLETED: [20, 40]}},
        start_date=datetime.today().strftime("%Y-%m-%d"),
    )
    ds_result = vaccine_backfills.estimate_initiated_from_state_ratio(ds_in)
    derived = test_helpers.make_tag(
        TagType.DERIVED, function_name="estimate_initiated_from_state_ratio"
    )
    ds_expected = test_helpers.build_dataset(
        {
            **metrics_unmodified_regions,
            region_no: {
                CommonFields.VACCINATIONS_COMPLETED: [20, 40],
                CommonFields.VACCINATIONS_INITIATED: TimeseriesLiteral(
                    [10, 30], annotation=[derived]
                ),
            },
        },
        start_date=datetime.today().strftime("%Y-%m-%d"),
    )
    test_helpers.assert_dataset_like(ds_result, ds_expected)