Airflow v2.0b3
 Kubernetes v1.19.3

Discovered issue while testing KubernetesPodOperator (haven't tested with other operator).
If I create a multiline string using """ """", add some variables inside (Jinja templating), then use this string as an argument to KubernetesPodOperator:
- In Graph View DAG is not visible (just gray area where it should be a digraph);
- in browser's web console i see the following error:

`Uncaught TypeError: node is undefined
    preProcessGraph http://localhost:8080/static/dist/dagre-d3.min.js:103
    preProcessGraph http://localhost:8080/static/dist/dagre-d3.min.js:103
    fn http://localhost:8080/static/dist/dagre-d3.min.js:103
    call http://localhost:8080/static/dist/d3.min.js:3
    draw http://localhost:8080/graph?dag_id=mydag&execution_date=mydate
    expand_group http://localhost:8080/graph?dag_id=mydag&execution_date=mydate
    <anonymous> http://localhost:8080/graph?dag_id=mydag&execution_date=mydate`

Tree view works without issues in this case. The DAG succeeds.
tests/utils/test_task_group.py
execution_date = pendulum.parse("20200101")
    with DAG("test_build_task_group_context_manager", start_date=execution_date) as dag:
        task1 = DummyOperator(task_id="task1")
        with TaskGroup("group234") as group234:
            _ = DummyOperator(task_id="task2")
            with TaskGroup("group34") as group34:
                _ = DummyOperator(task_id="task3")
                _ = DummyOperator(task_id="task4")
        task5 = DummyOperator(task_id="task5")
        task1 >> group234
        group34 >> task5
    assert task1.get_direct_relative_ids(upstream=False) == {
        'group234.group34.task4',
        'group234.group34.task3',
        'group234.task2',
    }
    assert task5.get_direct_relative_ids(upstream=True) == {
        'group234.group34.task4',
        'group234.group34.task3',
    }
    assert dag.task_group.group_id is None
    assert dag.task_group.is_root
    assert set(dag.task_group.children.keys()) == {"task1", "group234", "task5"}
    assert group34.group_id == "group234.group34"
    assert task_group_to_dict(dag.task_group) == EXPECTED_JSON
def test_build_task_group():