Attibutes are 'disappearing' from CBV. Django

I am trying to build CBV with class View parent. This view takes slug of object and find that object between two django models. The functions from services.py was doing a lot of DB queries, so, I tried to reduce them by giving to FeedbackSection necessary attributes(slug, model_instance and context) and lately override them in get method.

class FeedbackSection(View):
    """
    Feedback section for different objects.

    This is something like 'generic' view, so I implement it that it will find
    the model and feedbacks for this model by having only slug.
    """

    template_name = 'feedbacks/feedback-section.html'
    form_class = CreateFeedbackForm
    slug = None
    model_instance = None
    context = None

    def get(self, request, *args, **kwargs):
        self.slug = kwargs.get('slug')
        self.model_instance = get_model_instance(self.slug)
        self.context = get_feedback_section_context(self.slug, self.form_class, self.model_instance)
        return render(request, self.template_name, self.context)

    @method_decorator(login_required)
    def post(self, request, *args, **kwargs):
        form = self.form_class(request.POST)
        if form.is_valid():
            # will create feedback object and update model[Advert, Company] rating.
            end_feedback_post_logic(self.request.user, form, self.model_instance)
        return render(request, self.template_name, self.context)

The attributes(slug, model_instance and context), when post method is in runtime are equivalent to None. The problem is that this implementation was working fine yesterday, but today it's not.

I know I can use my functions again, but in post method. I don't want to do this. Because it will multiple DB Queries by two.

We need to override the setup method of the View class and define those attributes there.

def setup(self, request, *args, **kwargs):
    self.slug = kwargs.get('slug')
    self.model_instance = get_model_instance(self.slug)
    self.context = get_feedback_section_context(
        self.slug,
        self.form_class,
        self.model_instance
    )
    return super().setup(request, *args, **kwargs)
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