code: def get_active_topics_count(last_seen_timestamp=None):
      
      if not last_seen_timestamp:
          last_seen_timestamp = yesterday_timestamp()
      return Topic.objects.filter(modified_int__gt=last_seen_timestamp).count()
docs: Returns count of new topics since last visit, or one day.
      {% get_active_topics_count as active_topic_count %}