**Apache Airflow version**: 2.1.1

**What happened**:

The rendered templates screen doesn't show the operator arguments for TaskFlow API operators.
![image](https://user-images.githubusercontent.com/72943478/125486179-f6dde0be-9f60-4aca-831a-5cfd16e7f006.png)

**What you expected to happen**:

Should show the arguments after any templates have been rendered.

**How to reproduce it**:

Will happen for any `@task` decorated operator.

**Anything else we need to know**:

This issue appears on a number of operators.  Possible solution is to modify the "get_python_source" in utils/code_utils.py to handle list and dict. This would cause any operator that using py as the renderer to handle lists and dicts.  Possibly something like:
```
    if isinstance(x, list):
        return [str(v) for v in x]

    if isinstance(x, dict):
        return {k: str(v) for k, v in x.items()}
```
The converting values to strings seems necessary in order to avoid errors when this is passed to the pygments lexer.
![image](https://user-images.githubusercontent.com/72943478/125494716-01cf0c11-9e5f-45fa-afe2-4f99409edefc.png)

airflow/www/views.py
return self.render_template(
                    'airflow/trigger.html', dag_id=dag_id, origin=origin, conf=request_conf, form=form
                )
        dag = current_app.dag_bag.get_dag(dag_id)
        dag.create_dagrun(
            run_type=DagRunType.MANUAL,
            execution_date=execution_date,
            state=State.QUEUED,
            conf=run_conf,
            external_trigger=True,
            dag_hash=current_app.dag_bag.dags_hash.get(dag_id),
        )
        flash(f"Triggered {dag_id}, it should start any moment now.")
        return redirect(origin)
    def _clear_dag_tis(
        self, dag, start_date, end_date, origin, recursive=False, confirmed=False, only_failed=False
    ):
        if confirmed:
            count = dag.clear(
                start_date=start_date,
                end_date=end_date,
                include_subdags=recursive,
                include_parentdag=recursive,
                only_failed=only_failed,
            )
            flash(f"{count} task instances have been cleared")
            return redirect(origin)
        try:
            tis = dag.clear(
                start_date=start_date,