(optional LST_DUMMY_DATA as nullable list, 
 optional LST_COLUMNS    as nullable list) as table => 
    let
        DummyColumns = if LST_COLUMNS = null then LST_DUMMY_DATA else LST_COLUMNS,
        DummyData = if LST_DUMMY_DATA = null then List.Repeat({null}, List.Count(DummyColumns)) else LST_DUMMY_DATA,
        Dummy = #table(DummyColumns, {DummyData})
    in
        Dummy