# Buggy code
def init_on_load(self):
    """
    Called by the ORM after the instance has been loaded from the DB or otherwise reconstituted
    i.e automatically deserialize Xcom value when loading from DB.
    """
    try:
        self.value = XCom.deserialize_value(self)
    except (UnicodeEncodeError, ValueError):
        # For backward-compatibility.
        # Preventing errors in webserver
        # due to XComs mixed with pickled and unpickled.
        self.value = pickle.loads(self.value)


# Traceback (ValueError)
Python version: 3.8.6
Airflow version: 2.0.0b2
Node: 950a17127708
-------------------------------------------------------------------------------
Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
response = self.full_dispatch_request()
File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/usr/local/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
raise value
File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/security/decorators.py", line 109, in wraps
return f(self, *args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/views.py", line 552, in list
return self.render_template(
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/baseviews.py", line 280, in render_template
return render_template(
File "/usr/local/lib/python3.8/site-packages/flask/templating.py", line 137, in render_template
return _render(
File "/usr/local/lib/python3.8/site-packages/flask/templating.py", line 120, in _render
rv = template.render(context)
File "/usr/local/lib/python3.8/site-packages/jinja2/environment.py", line 1090, in render
self.environment.handle_exception()
File "/usr/local/lib/python3.8/site-packages/jinja2/environment.py", line 832, in handle_exception
reraise(*rewrite_traceback_stack(source=source))
File "/usr/local/lib/python3.8/site-packages/jinja2/_compat.py", line 28, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/general/model/list.html", line 2, in top-level template code
{% import 'appbuilder/general/lib.html' as lib %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/base.html", line 1, in top-level template code
{% extends base_template %}
File "/opt/airflow/airflow/www/templates/airflow/master.html", line 20, in top-level template code
{% extends 'appbuilder/baselayout.html' %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/baselayout.html", line 2, in top-level template code
{% import 'appbuilder/baselib.html' as baselib %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/init.html", line 46, in top-level template code
{% block body %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/baselayout.html", line 19, in block "body"
{% block content %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/general/model/list.html", line 13, in block "content"
{% block list_list scoped %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/general/model/list.html", line 15, in block "list_list"
{{ widgets.get('list')()|safe }}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/widgets.py", line 37, in __call__
return template.render(args)
File "/usr/local/lib/python3.8/site-packages/jinja2/environment.py", line 1090, in render
self.environment.handle_exception()
File "/usr/local/lib/python3.8/site-packages/jinja2/environment.py", line 832, in handle_exception
reraise(*rewrite_traceback_stack(source=source))
File "/usr/local/lib/python3.8/site-packages/jinja2/_compat.py", line 28, in reraise
raise value.with_traceback(tb)
File "/opt/airflow/airflow/www/templates/airflow/model_list.html", line 21, in top-level template code
{% extends 'appbuilder/general/widgets/base_list.html' %}
File "/usr/local/lib/python3.8/site-packages/flask_appbuilder/templates/appbuilder/general/widgets/base_list.html", line 23, in top-level template code
{% block begin_loop_values %}
File "/opt/airflow/airflow/www/templates/airflow/model_list.html", line 80, in block "begin_loop_values"
{% elif item[value] != None %}
File "/usr/local/lib/python3.8/site-packages/pandas/core/generic.py", line 1326, in __nonzero__
raise ValueError(
ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

# Fixed code
def init_on_load(self):
    """
    Called by the ORM after the instance has been loaded from the DB or otherwise reconstituted
    i.e automatically deserialize Xcom value when loading from DB.
    """
    try:
        self.value = self.orm_deserialize_value()
    except (UnicodeEncodeError, ValueError):
        # For backward-compatibility.
        # Preventing errors in webserver
        # due to XComs mixed with pickled and unpickled.
        self.value = pickle.loads(self.value)