code: def _merge_cluster(self, c2keep, c2empty):
          r
          while len(self.queue[c2empty]) > 0:
              temp = [_pc, _id, _type] = hq.heappop(self.queue[c2empty])
              if self[_type+'.invasion_sequence'][_id] == -1:
                  hq.heappush(self.queue[c2keep], temp)
          self.invasion_running[c2empty] = False
docs: r"""
          Little helper function to merger clusters but only add the uninvaded
          elements