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
{'id': 'group234.task_2'},
                    {'id': 'group234.task_3'},
                    {'id': 'group234.task_4'},
                    {'id': 'group234.upstream_join_id'},
                    {'id': 'group234.downstream_join_id'},
                ],
            },
            {'id': 'task_1'},
            {'id': 'task_5'},
        ],
    }
    edges = dag_edges(dag)
    assert sorted((e["source_id"], e["target_id"]) for e in edges) == [
        ('group234.downstream_join_id', 'task_5'),
        ('group234.task_2', 'group234.task_4'),
        ('group234.task_3', 'group234.task_4'),
        ('group234.task_4', 'group234.downstream_join_id'),
        ('group234.upstream_join_id', 'group234.task_2'),
        ('group234.upstream_join_id', 'group234.task_3'),
        ('task_1', 'group234.upstream_join_id'),
    ]
def test_sub_dag_task_group():
    """
    Tests dag.sub_dag() updates task_group correctly.
    """
    execution_date = pendulum.parse("20200101")
    with DAG("test_test_task_group_sub_dag", start_date=execution_date) as dag:
        task1 = DummyOperator(task_id="task1")
        with TaskGroup("group234") as group234:
            _ = DummyOperator(task_id="task2")