code: def test_xcom_not_iterable(self, dag_maker):
      python_op = build_python_op(dag_maker)
      actual = XComArg(python_op)
      with pytest.raises(TypeError) as ctx:
          list(actual)
      assert str(ctx.value) == "'XComArg' object is not iterable"
  
imports: from __future__ import annotations
  import pytest
  from airflow.models.xcom_arg import XComArg
  from airflow.operators.bash import BashOperator
  from airflow.operators.python import PythonOperator
  from airflow.utils.types import NOTSET
  from tests.test_utils.config import conf_vars
  from tests.test_utils.db import clear_db_dags, clear_db_runs
label_desc: Use image node_id 8 for calling the TestXComArgBuild obj's underlying member method code with example usage: obj.test_xcom_not_iterable(dag_maker) without return types