docs: def get_new_topics_count(last_seen=None, for_member=False):
      """
      Returns count of new topics since last visit, or one day.
      {% get_new_topics_count as new_topic_count %}
      """
      if not last_seen:
          last_seen = yesterday()
      if not for_member:
          return Topic.objects.filter(created__gt=last_seen).count()
      return Topic.objects.filter(modified__gt=last_seen, user__id=for_member).count()