class LessonListMixin(object):
    def get_context_data(self, **kwargs):
        context = super(LessonListMixin, self).get_context_data(**kwargs)
        context['lesson_list'] = self.get_lesson_list()
        return context

    def get_lesson_list(self):
        form = DateForm(data=self.request.GET)
        date = form.get_cleaned_date()
        week_start = date - datetime.timedelta(date.weekday())
        week_end = week_start + datetime.timedelta(6)
        return self.object.lesson_set.filter(date__range=[week_start, week_end]).select_related()