code: def test_add_to_sub_group():
      with DAG("test_dag", start_date=pendulum.parse("20200101")):
          tg = TaskGroup("section")
          task = EmptyOperator(task_id="task")
          with pytest.raises(TaskAlreadyInTaskGroup) as ctx:
              tg.add(task)
  
      assert (
          str(ctx.value)
          == "cannot add 'task' to 'section' (already in the DAG's root group)"
      )
  
imports: from __future__ import annotations
  from datetime import timedelta
  import pendulum
  import pytest
  from airflow.decorators import dag, setup, task, task_group, teardown
  from airflow.exceptions import TaskAlreadyInTaskGroup
  from airflow.models.baseoperator import BaseOperator
  from airflow.models.dag import DAG
  from airflow.models.xcom_arg import XComArg
  from airflow.operators.bash import BashOperator
  from airflow.operators.empty import EmptyOperator
  from airflow.operators.python import PythonOperator
  from airflow.utils.dag_edges import dag_edges
  from airflow.utils.task_group import TaskGroup, task_group_to_dict
  from tests.models import DEFAULT_DATE
label_desc: Use image node_id 28 for calling a global function with example usage: test_add_to_sub_group() without return types