How to use the dataflows.checkpoint function in dataflows

def run_data_count_flow():
        assert Flow(
            get_data_count_views(),
            checkpoint('test_checkpoint'),
        ).results()[0] == [[{'foo': 'bar'}]]

def test_load_from_checkpoint():
    from dataflows import Flow, checkpoint
    import shutil

    shutil.rmtree('.checkpoints/test_load_from_checkpoint', ignore_errors=True)

    assert Flow(
        [{'foo': 'bar'}],
        checkpoint('test_load_from_checkpoint')
    ).process()

    assert Flow(
        checkpoint('test_load_from_checkpoint')
    ).results()[0] == [[{'foo': 'bar'}]]

def test_load_from_checkpoint():
    from dataflows import Flow, checkpoint
    import shutil

    shutil.rmtree('.checkpoints/test_load_from_checkpoint', ignore_errors=True)

    assert Flow(
        [{'foo': 'bar'}],
        checkpoint('test_load_from_checkpoint')
    ).process()

    assert Flow(
        checkpoint('test_load_from_checkpoint')
    ).results()[0] == [[{'foo': 'bar'}]]

import shutil

    dates = [
        datetime.now(),
        datetime.now(timezone.utc).astimezone()
    ]

    shutil.rmtree('.checkpoints/test_load_dates_timezones', ignore_errors=True)

    Flow(
        [{'date': d.date(), 'datetime': d} for d in dates],
        checkpoint('test_load_dates_timezones')
    ).process()

    results = Flow(
        checkpoint('test_load_dates_timezones')
    ).results()

    assert list(map(lambda x: x['date'], results[0][0])) == \
        list(map(lambda x: x.date(), dates))
    assert list(map(lambda x: x['datetime'], results[0][0])) == \
        list(map(lambda x: x, dates))

def test_load_dates_timezones():
    from dataflows import Flow, checkpoint
    from datetime import datetime, timezone
    import shutil

    dates = [
        datetime.now(),
        datetime.now(timezone.utc).astimezone()
    ]

    shutil.rmtree('.checkpoints/test_load_dates_timezones', ignore_errors=True)

    Flow(
        [{'date': d.date(), 'datetime': d} for d in dates],
        checkpoint('test_load_dates_timezones')
    ).process()

    results = Flow(
        checkpoint('test_load_dates_timezones')
    ).results()

    assert list(map(lambda x: x['date'], results[0][0])) == \
        list(map(lambda x: x.date(), dates))
    assert list(map(lambda x: x['datetime'], results[0][0])) == \
        list(map(lambda x: x, dates))

def main_flow(prefix, operator):
    return Flow(
        cluster_info(operator),
        update_resource(['res_1'], name='cluster-info', path='cluster-info.csv'),
        checkpoint(f'{prefix}-cluster-info'),
        ckan_cloud_instances(operator),
        update_resource(['res_2'], name='ckan-cloud-instances', path='ckan-cloud-instances.csv'),
    )