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
self,
        start_date: Optional[datetime] = None,
        end_date: Optional[datetime] = None,
        upstream: bool = False,
        downstream: bool = False,
        session: Session = None,
    ):
        """
        Clears the state of task instances associated with the task, following
        the parameters specified.
        """
        qry = session.query(TaskInstance).filter(TaskInstance.dag_id == self.dag_id)
        if start_date:
            qry = qry.filter(TaskInstance.execution_date >= start_date)
        if end_date:
            qry = qry.filter(TaskInstance.execution_date <= end_date)
        tasks = [self.task_id]
        if upstream:
            tasks += [t.task_id for t in self.get_flat_relatives(upstream=True)]
        if downstream:
            tasks += [t.task_id for t in self.get_flat_relatives(upstream=False)]
        qry = qry.filter(TaskInstance.task_id.in_(tasks))
        results = qry.all()
        count = len(results)
        clear_task_instances(results, session, dag=self.dag)
        session.commit()
        return count
    @provide_session
    def get_task_instances(