unable to import rest_framework_simplejwt

I have installed djangorestframework-simplejwt package and trying to import that module in urls.py and views.py but still its not working. Please guide me to solve this issue.

pip list

Package                       Version
----------------------------- -------
asgiref                       3.3.1
Django                        3.1.4
djangorestframework           3.12.2
djangorestframework-simplejwt 4.6.0
pip                           20.2.3
PyJWT                         1.7.1
pytz                          2020.4
setuptools                    49.2.1
sqlparse                      0.4.1

Settings.py

INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'Django_MedicalApp',
'rest_framework',
'rest_framework_simplejwt',]


REST_FRAMEWORK = {'DEFAULT_AUTHENTICATION_CLASSES':
                  ['rest_framework_simplejwt.authentication.JWTAuthentication',],
              'DEFAULT_PERMISSION_CLASSES': 
('rest_framework.permissions.AllowAny','rest_framework.permissions.IsAuthenticatedOrReadOnly',)}

urls.py

from rest_framework_simplejwt.views import TokenObtainPairView
router = routers.DefaultRouter()
router.register('Company',views.CompanyViewset,basename='Company')


urlpatterns = [
path('admin/', admin.site.urls),
path('api/',include(router.urls),
path('api/token/', TokenObtainPairView.as_view(), name='token_obtain_pair'))]

views.py

from rest_framework_simplejwt.authentication import JWTAuthentication

class CompanyViewset(viewsets.ViewSet):
    authentication_classes = [JWTAuthentication]

Please help me to resolve this import error.