Python/Django 'Type object is not iterable' Django Rest Framework (DRF)

I'm trying to GET fetch my REST API in DRF, but keep getting the error below. What could be the problem? Thanks!

Internal Server Error: /polls/
.....
.....
TypeError: 'type' object is not iterable
[08/Aug/2021 07:02:50] "GET /polls/ HTTP/1.1" 500 100344
Not Found: /favicon.ico
[08/Aug/2021 07:02:53] "GET /favicon.ico HTTP/1.1" 404 3415

The apiviews code: apiviews.py

class PollList(generics.ListCreateAPIView):
    queryset = Poll.objects.all()
    serializer_class = PollSerializer

The polls code: models.py

class Poll(models.Model):
    question = models.CharField(max_length=100)
    created_by = models.ForeignKey(User, on_delete=models.CASCADE)
    pub_date = models.DateTimeField(auto_now=True)

Serializer.py:

class PollSerializer(serializers.ModelSerializer):
    choices = ChoiceSerializer(many=True, read_only=True, required=False)
    
    class Meta:
        model = Poll
        fields = '__all__'

urls.py:

urlpatterns = [
    path("polls/", PollList.as_view(), name="polls_list"),
]

Admin URLs:

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path(r'^', include('vote.urls')),
]

Here's portions of the traceback:

Internal Server Error: /polls/
Traceback (most recent call last):
  File "D:\Studio\Python\REST\elections\env\lib\site-packages\django\core\handlers\exception.py", line 35, in inner 
....
....
\rest_framework\views.py", line 400, in initial        
    self.check_permissions(request)
  File "D:\Studio\Python\REST\elections\env\lib\site-packages\rest_framework\views.py", line 332, in check_permissions
    for permission in self.get_permissions():
  File "D:\Studio\Python\REST\elections\env\lib\site-packages\rest_framework\views.py", line 279, in get_permissions    return [permission() for permission in self.permission_classes]
TypeError: 'type' object is not iterable

Here's the Settings.py code implementing the Authentication:

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework.authentication.TokenAuthentication',
        'rest_framework.authentication.SessionAuthentication'
    ),
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticated'
    )
}

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    ....
    ....
]