Django. Sinleton admin mixin

admin.py

class SingleObjectAdminModelMixin(AdminCharCountMixin):
    list_display = ('page_name',)

    def has_delete_permission(self, request, obj=None):
        """
        Forbid object deleting
        """
        return True

    def page_name(self, obj):
        """
        Displaying model verbose name as single-object name
        :param obj:
        :return:
        """
        return obj._meta.verbose_name

    def get_object_info(self):
        """
        Getting app name and model name to build urls for adding and changing single object
        :param obj: page object
        :return: name of app, name of model
        """
        name = self.model._meta.model_name
        app_name = self.model._meta.app_label
        return name, app_name

    # taken from preferences app
    def changelist_view(self, *args, **kwargs):
        """
        Redirects on changelist_view get request.
        If no object - to create page
        Otherwise - to change page of some object
        """
        obj = self.model.objects.only('id').first()
        if not obj:
            obj = self.model.objects.create()
        name, app_name = self.get_object_info()
        return HttpResponseRedirect(
            reverse('admin:{}_{}_change'.format(app_name, name), args=[obj.id])
        )

    def response_change(self, request, obj, post_url_continue=None):
        """
        Redirects after object's change to its change page
        Actually it's just a reload
        """
        name, app_name = self.get_object_info()
        return HttpResponseRedirect(
            reverse('admin:{}_{}_change'.format(app_name, name), args=[obj.id])
        )

    def response_add(self, request, obj, post_url_continue=None):
        """
        Redirects to the change page of the created object.
        Does not allow to add new objects.
        If user clicks on "Save and add another", we just redirect to change view 
        """
        name, app_name = self.get_object_info()
        return HttpResponseRedirect(
            reverse('admin:{}_{}_change'.format(app_name, name), args=[obj.id])
        )