class ListSites(ListView):
    model = Sites
    context_object_name = 'sites'
    template_name = 'sites/list_sites.html'
    paginate_by = 18
    def get_context_data(self, **kwargs):
        context = super(ListSites, self).get_context_data(**kwargs)
        if self.request.session.get("order"):
            context['sites'] = Sites.objects.all().order_by(self.request.session["order"])
        return context