def METHOD_NAME(vd):
    t = make_tester('''
            open-file sample_data/sample.tsv
            +::OrderDate key-col
            +::Region key-col
            +::Rep key-col
        ''')
    t('',                             'OrderDate Region Rep Item Units Unit_Cost Total')
    t('+::Rep slide-leftmost',        'Rep OrderDate Region Item Units Unit_Cost Total')
    t('+::OrderDate slide-rightmost', 'Region Rep OrderDate Item Units Unit_Cost Total')
    t('+::Rep slide-left',            'OrderDate Rep Region Item Units Unit_Cost Total')
    t('+::OrderDate slide-right',     'Region OrderDate Rep Item Units Unit_Cost Total')
    t('''
        +::Item key-col
        +::Item slide-left
        slide-left
        slide-right
        slide-right
        slide-left
        slide-left
    ''', 'OrderDate Item Region Rep Units Unit_Cost Total')