code: def push(self, instance, action, success, idxs=_marker):
          
          uid = api.get_uid(instance)
          info = self.objects.get(uid, {})
          idx = [] if idxs is _marker else idxs
          info[action] = {'success': success, 'idxs': idx}
          self.objects[uid] = info
docs: Adds an instance into the pool, to be reindexed on resume