**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
"""View to show Airflow Plugins"""
    default_view = 'list'
    class_permission_name = permissions.RESOURCE_PLUGIN
    method_permission_name = {
        'list': 'read',
    }
    base_permissions = [
        permissions.ACTION_CAN_READ,
        permissions.ACTION_CAN_ACCESS_MENU,
    ]
    plugins_attributes_to_dump = [
        "hooks",
        "executors",
        "macros",
        "admin_views",
        "flask_blueprints",
        "menu_links",
        "appbuilder_views",
        "appbuilder_menu_items",
        "global_operator_extra_links",
        "operator_extra_links",
        "source",
    ]
    @expose('/plugin')
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_PLUGIN),
        ]
    )
    def list(self):