**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
)
from flask_appbuilder.widgets import FormWidget
from flask_babel import lazy_gettext
from jinja2.utils import htmlsafe_json_dumps, pformat  
from pendulum.datetime import DateTime
from pendulum.parsing.exceptions import ParserError
from pygments import highlight, lexers
from pygments.formatters import HtmlFormatter
from sqlalchemy import Date, and_, desc, func, or_, union_all
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import joinedload
from wtforms import SelectField, validators
from wtforms.validators import InputRequired
import airflow
from airflow import models, plugins_manager, settings
from airflow.api.common.experimental.mark_tasks import (
    set_dag_run_state_to_failed,
    set_dag_run_state_to_success,
)
from airflow.configuration import AIRFLOW_CONFIG, conf
from airflow.exceptions import AirflowException
from airflow.executors.executor_loader import ExecutorLoader
from airflow.jobs.base_job import BaseJob
from airflow.jobs.scheduler_job import SchedulerJob
from airflow.models import DAG, Connection, DagModel, DagTag, Log, SlaMiss, TaskFail, XCom, errors
from airflow.models.baseoperator import BaseOperator
from airflow.models.dagcode import DagCode
from airflow.models.dagrun import DagRun, DagRunType
from airflow.models.serialized_dag import SerializedDagModel
from airflow.models.taskinstance import TaskInstance