Ensure that this works:

```python
@setup
def mytask():
    print("I am a setup task")

with dag_maker() as dag:
    mytask.override(task_id='newtask')

assert len(dag.task_group.children) == 1
setup_task = dag.task_group.children["newtask"]
assert setup_task._is_setup
```
and teardown also works
tg.expand(a=[".", ".."])
    ser_dag = SerializedBaseOperator.serialize(dag)
    assert ser_dag["_task_group"]["children"]["tg"] == (
        "taskgroup",
        {
            "_group_id": "tg",
            "children": {
                "tg.op1": ("operator", "tg.op1"),
                # "tg.op2": ("operator", "tg.op2"),
            },
            "downstream_group_ids": [],
            "downstream_task_ids": [],
            "expand_input": {
                "type": "dict-of-lists",
                "value": {"__type": "dict", "__var": {"a": [".", ".."]}},
            },
            "is_mapped": True,
            "prefix_group_id": True,
            "tooltip": "",
            "ui_color": "CornflowerBlue",
            "ui_fgcolor": "#000",
            "upstream_group_ids": [],
            "upstream_task_ids": [],
        },
    )
    serde_dag = SerializedDAG.deserialize_dag(ser_dag)
    serde_tg = serde_dag.task_group.children["tg"]
    assert isinstance(serde_tg, MappedTaskGroup)
    assert serde_tg._expand_input == DictOfListsExpandInput({"a": [".", ".."]})