code: def get_threads_where_participant_is_active(self, participant_id):
          
          participations = Participation.objects.\
              filter(participant__id=participant_id).\
              exclude(date_left__lte=now()).\
              distinct().\
              select_related('thread')
  
          return Thread.objects.\
              filter(id__in=[p.thread.id for p in participations]).\
              distinct()
docs: Gets all the threads in which the current participant is involved. The method excludes threads where the participant has left.