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.
airflow/models/baseoperator.py
"""
        Set a task or a task list to be directly downstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=False)
    def set_upstream(self, task_or_task_list: Union[TaskMixin, Sequence[TaskMixin]]) -> None:
        """
        Set a task or a task list to be directly upstream from the current
        task. Required by TaskMixin.
        """
        self._set_relatives(task_or_task_list, upstream=True)
    @property
    def output(self):