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
from airflow.models.xcom_arg import PlainXComArg, XComArg
    from airflow.serialization.serialized_objects import _XComRef
    with DAG("test-dag", start_date=datetime(2020, 1, 1)) as dag:
        task1 = BaseOperator(task_id="op1")
        mapped = MockOperator.partial(task_id="task_2").expand(arg2=XComArg(task1))
    serialized = SerializedBaseOperator.serialize(mapped)
    assert serialized == {
        "_is_empty": False,
        "_is_mapped": True,
        "_task_module": "tests.test_utils.mock_operators",
        "_task_type": "MockOperator",