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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def post(self, request):
 """Validate and process the login POST request."""

        """Before September 1st, do not allow Class of [year+4] to log in."""
        if request.POST.get("username", "").startswith(str(date.today().year + 4)) and date.today() < settings.SCHOOL_START_DATE:
            return index_view(request, added_context={"auth_message": "Your account is not yet active for use with this application."})

        form = AuthenticateForm(data=request.POST)

        if request.session.test_cookie_worked():
            request.session.delete_test_cookie()
        else:
            logger.warning("No cookie support detected! This could cause problems.")

        if form.is_valid():
            reset_user, status = User.objects.get_or_create(username="RESET_PASSWORD", user_type="service", id=999999)
            if form.get_user() == reset_user:
                return redirect(reverse("reset_password") + "?expired=True")
            login(request, form.get_user())
            # Initial load into session
            logger.info("Login succeeded as {}".format(request.POST.get("username", "unknown")))
            logger.info("request.user: {}".format(request.user))

            log_auth(request, "success{}".format(" - first login" if not request.user.first_login else ""))

            default_next_page = "index"

            if request.user.is_eighthoffice:
                """Default to eighth admin view (for eighthoffice)."""
                default_next_page = "eighth_admin_dashboard"

            # if request.user.is_eighthoffice:
            #    """Eighthoffice's session should (almost) never expire."""
            #    request.session.set_expiry(timezone.now() + timedelta(days=30))

            if not request.user.first_login:
                logger.info("First login")
                request.user.first_login = make_aware(datetime.now())
                request.user.save()
                request.session["first_login"] = True

                if request.user.is_student or request.user.is_teacher:
                    default_next_page = "welcome"
                else:
                    pass  # exclude eighth office/special accounts

            # if the student has not seen the 8th agreement yet, redirect them
            if request.user.is_student and not request.user.seen_welcome:
                return redirect("welcome")

            next_page = request.POST.get("next", request.GET.get("next", default_next_page))
            return redirect(next_page)
        else:
            log_auth(request, "failed")
            logger.info("Login failed as {}".format(request.POST.get("username", "unknown")))
            return index_view(request, auth_form=form)