**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
"""Clears the Dag."""
        dag_id = request.form.get('dag_id')
        task_id = request.form.get('task_id')
        origin = get_safe_url(request.form.get('origin'))
        dag = current_app.dag_bag.get_dag(dag_id)
        execution_date = request.form.get('execution_date')
        execution_date = timezone.parse(execution_date)
        confirmed = request.form.get('confirmed') == "true"
        upstream = request.form.get('upstream') == "true"
        downstream = request.form.get('downstream') == "true"
        future = request.form.get('future') == "true"
        past = request.form.get('past') == "true"
        recursive = request.form.get('recursive') == "true"
        only_failed = request.form.get('only_failed') == "true"
        dag = dag.partial_subset(
            task_ids_or_regex=fr"^{task_id}$",
            include_downstream=downstream,
            include_upstream=upstream,
        )
        end_date = execution_date if not future else None
        start_date = execution_date if not past else None
        return self._clear_dag_tis(
            dag,
            start_date,
            end_date,
            origin,
            recursive=recursive,
            confirmed=confirmed,