**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
'external_trigger',
        'conf',
    ]
    search_columns = [
        'state',
        'dag_id',
        'execution_date',
        'run_id',
        'run_type',
        'start_date',
        'end_date',
        'external_trigger',
    ]
    edit_columns = ['state', 'dag_id', 'execution_date', 'start_date', 'end_date', 'run_id', 'conf']
    base_order = ('execution_date', 'desc')
    base_filters = [['dag_id', DagFilter, lambda: []]]
    add_form = DagRunForm
    edit_form = DagRunEditForm
    formatters_columns = {
        'execution_date': wwwutils.datetime_f('execution_date'),
        'state': wwwutils.state_f,
        'start_date': wwwutils.datetime_f('start_date'),
        'end_date': wwwutils.datetime_f('end_date'),
        'dag_id': wwwutils.dag_link,
        'run_id': wwwutils.dag_run_link,
        'conf': wwwutils.json_f('conf'),
    }
    @action('muldelete', "Delete", "Are you sure you want to delete selected records?", single=False)
    @provide_session
    def action_muldelete(self, items, session=None):