          False: False,
          None: None,
          'other': True
      }
      field = serializers.NullBooleanField()
  
  
  class TestNullableBooleanField(TestNullBooleanField):
      """
      Valid and invalid values for `BooleanField` when `allow_null=True`.
 
</s> remove             url(r'^example/?$', views.ExampleListView.as_view()),
            url(r'^example/(?P<pk>\d+)/?$', views.ExampleDetailView.as_view()),
            url(r'^example/(?P<pk>\d+)/sub/?$', views.ExampleDetailView.as_view()),
 </s> add             path('example/', views.ExampleListView.as_view()),
            path('example/<int:pk>/', views.ExampleDetailView.as_view()),
            path('example/<int:pk>/sub/', views.ExampleDetailView.as_view()), </s> remove             url(r'^', include(router.urls))
 </s> add             path('', include(router.urls)) </s> remove             url(r'^example/?$', views.ExampleAutoSchemaComponentName.as_view()),
 </s> add             path('example/', views.ExampleAutoSchemaComponentName.as_view()), </s> remove             url('^example/?$', views.ExampleListView.as_view()),
            url(r'^', include(router.urls))
 </s> add             path('example/', views.ExampleListView.as_view()),
            path('', include(router.urls)) </s> remove from django.conf.urls import url
 </s> add from django.urls import path
    field = serializers.BooleanField(allow_null=True)
          False: False,
          None: None,
          'other': True
      }
    field = serializers.BooleanField(allow_null=True)
  
  
  class TestNullableBooleanField(TestNullBooleanField):
      """
      Valid and invalid values for `BooleanField` when `allow_null=True`.
keep keep keep keep replace keep keep keep keep keep
 Replace all url() calls with path() or re_path() (#7512)

* url() is deprecated in Django 3.1

* update given feedbacks on url() is deprecated in Django 3.1

* Fix test_urlpatterns.py to continue testing mixed re_path() and path()

* Fix one missed reference

Co-authored-by: sanjusci <sanju.sci9@gmail.com> 
tests/test_fields.py