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.decorators import task
    from airflow.models.xcom_arg import XComArg
    from airflow.serialization.serialized_objects import _ExpandInputRef, _XComRef
    with DAG("test-dag", start_date=datetime(2020, 1, 1)) as dag:
        op1 = BaseOperator(task_id="op1")
        @task(retry_delay=30)
        def x(arg1, arg2, arg3):
            print(arg1, arg2, arg3)
        print("**", type(x), type(x.partial), type(x.expand))
        x.partial(arg1=[1, 2, {"a": "b"}]).expand(arg2={"a": 1, "b": 2}, arg3=XComArg(op1))
    original = dag.get_task("x")
    serialized = SerializedBaseOperator.serialize(original)
    assert serialized == {
        "_is_empty": False,
        "_is_mapped": True,
        "_task_module": "airflow.decorators.python",
        "_task_type": "_PythonDecoratedOperator",