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
from airflow.models.dagparam import DagParam
        from airflow.models.xcom_arg import XComArg
        if isinstance(content, str):
            if any(content.endswith(ext) for ext in self.template_ext):
                
                return jinja_env.get_template(content).render(**context)
            else:
                return jinja_env.from_string(content).render(**context)
        elif isinstance(content, (XComArg, DagParam)):
            return content.resolve(context)
        if isinstance(content, tuple):
            if type(content) is not tuple:  
                
                return content.__class__(
                    *(self.render_template(element, context, jinja_env) for element in content)  
                )
            else:
                return tuple(self.render_template(element, context, jinja_env) for element in content)
        elif isinstance(content, list):
            return [self.render_template(element, context, jinja_env) for element in content]
        elif isinstance(content, dict):
            return {key: self.render_template(value, context, jinja_env) for key, value in content.items()}
        elif isinstance(content, set):
            return {self.render_template(element, context, jinja_env) for element in content}
        else:
            if seen_oids is None:
                seen_oids = set()
            self._render_nested_template_fields(content, context, jinja_env, seen_oids)
            return content
    def _render_nested_template_fields(