你好，我python3.6，django2.2，在登录时遇到这个问题AttributeError: ‘str’ object has no attribute ‘decode’。谢谢

Method Not Allowed: /login/
[10/Sep/2021 19:32:31] "GET /login/ HTTP/1.1" 405 7764
Internal Server Error: /login/
Traceback (most recent call last):
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\django\views\decorators\csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\django\views\generic\base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\views.py", line 480, in raise_uncaught_exception
    raise exc
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework_simplejwt\views.py", line 27, in post
    serializer.is_valid(raise_exception=True)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\serializers.py", line 220, in is_valid
    self._validated_data = self.run_validation(self.initial_data)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework\serializers.py", line 422, in run_validation
    value = self.validate(value)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework_simplejwt\serializers.py", line 75, in validate
    data['refresh'] = str(refresh)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework_simplejwt\tokens.py", line 82, in __str__
    return token_backend.encode(self.payload)
  File "C:\Users\Administrator\Envs\Shop\lib\site-packages\rest_framework_simplejwt\backends.py", line 43, in encode
    return token.decode('utf-8')
AttributeError: 'str' object has no attribute 'decode'
[10/Sep/2021 19:32:42] "POST /login/ HTTP/1.1" 500 128653