def METHOD_NAME(self):
    class MyTable(tables.Table):
        name = tables.Column()
    # this is obvious:
    self.assertEqual(list(MyTable(data).columns.columns.keys()), ["name"])
    self.assertEqual(
        list(
            MyTable(
                data, extra_columns=[("country", tables.Column()), ("name", None)]
            ).columns.columns.keys()
        ),
        ["country"],
    )
    # this new instance should not have the extra columns added to the first instance.
    self.assertEqual(list(MyTable(data).columns.columns.keys()), ["name"])