**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
"""Pre update hook."""
        item.execution_date = timezone.make_aware(item.execution_date)
        item.value = XCom.serialize_value(item.value)
def lazy_add_provider_discovered_options_to_connection_form():
    """Adds provider-discovered connection parameters as late as possible"""
    def _get_connection_types() -> List[Tuple[str, str]]:
        """Returns connection types available."""
        _connection_types = [
            ('fs', 'File (path)'),
            ('mesos_framework-id', 'Mesos Framework ID'),
        ]
        providers_manager = ProvidersManager()
        for connection_type, (_, _, _, hook_name) in providers_manager.hooks.items():
            _connection_types.append((connection_type, hook_name))
        return _connection_types
    ConnectionForm.conn_type = SelectField(
        lazy_gettext('Conn Type'),
        choices=sorted(_get_connection_types(), key=itemgetter(1)),
        widget=Select2Widget(),
        validators=[InputRequired()],
        description="""
            Conn Type missing?
            Make sure you've installed the corresponding Airflow Provider Package.
        """,
    )
    for key, value in ProvidersManager().connection_form_widgets.items():
        setattr(ConnectionForm, key, value.field)
class ConnectionFormWidget(FormWidget):