**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
"""Form widget used to display connection"""
    field_behaviours = json.dumps(ProvidersManager().field_behaviours)
class ConnectionModelView(AirflowModelView):
    """View to show records from Connections table"""
    route_base = '/connection'
    datamodel = AirflowModelView.CustomSQLAInterface(Connection)  
    class_permission_name = permissions.RESOURCE_CONNECTION
    method_permission_name = {
        'add': 'create',
        'list': 'read',
        'edit': 'edit',
        'delete': 'delete',
        'action_muldelete': 'delete',
        'action_mulduplicate': 'create',
    }
    base_permissions = [
        permissions.ACTION_CAN_CREATE,
        permissions.ACTION_CAN_READ,
        permissions.ACTION_CAN_EDIT,
        permissions.ACTION_CAN_DELETE,
        permissions.ACTION_CAN_ACCESS_MENU,
    ]
    extra_fields = list(ProvidersManager().connection_form_widgets.keys())
    list_columns = [
        'conn_id',
        'conn_type',