Repair the type annotations in the TokenViewBase class. (#880)

* Repair the type annotations in the TokenViewBase class.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Ah, python3.9 did support parameterizing the 'type' type.  I wasn't sure.  So we don't need the Type from typing.

* The abstract type is BaseSerializer, not Serializer

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: triplepoint

rest_framework_simplejwt/views.py

@@ -1,8 +1,10 @@
+from typing import Optional
+
 from django.utils.module_loading import import_string
 from rest_framework import generics, status
 from rest_framework.request import Request
 from rest_framework.response import Response
-from rest_framework.serializers import Serializer
+from rest_framework.serializers import BaseSerializer
 
 from .authentication import AUTH_HEADER_TYPES
 from .exceptions import InvalidToken, TokenError
@@ -13,12 +15,12 @@ class TokenViewBase(generics.GenericAPIView):
     permission_classes = ()
     authentication_classes = ()
 
-    serializer_class = None
+    serializer_class: Optional[type[BaseSerializer]] = None
     _serializer_class = ""
 
     www_authenticate_realm = "api"
 
-    def get_serializer_class(self) -> Serializer:
+    def get_serializer_class(self) -> type[BaseSerializer]:
         """
         If serializer_class is set, use it directly. Otherwise get the class from settings.
         """