Is depth-first execution applicable to task groups with both @task functions and classic opeators inside

[hongshibao]

Hi, I have a DAG with code similar with the below one:

@task()
def generate_ccommand(arg_1):
    # do sth
    return command

@task_group()
def my_tg(tg_arg):
    command = generate_ccommand(arg_1=tg_arg)
    docker_run_op = DockerOperator(command=command)
    command >> docker_run_op

@dag()
def my_dag():
    my_tg.expand(tg_arg=["arg_a", "arg_b", "arg_c"])

I tested it, and the task_group is expanded. And inside the task_group, generate_ccommand is also auto expanded, but the DockerOperator is not auto expanded. Is airflow not able to auto expand the classic operator in the above example? How can I achieve the depth-first execution for my task_group with classic opeators inside?