code: func (lc *LightChain) Rollback(chain []common.Hash) {
  	lc.chainmu.Lock()
  	defer lc.chainmu.Unlock()
  
  	for i := len(chain) - 1; i >= 0; i-- {
  		hash := chain[i]
  
  		if head := lc.hc.CurrentHeader(); head.Hash() == hash {
  			lc.hc.SetCurrentHeader(lc.GetHeader(head.ParentHash, head.Number.Uint64()-1))
  		}
  	}
  }
docs: // Rollback is designed to remove a chain of links from the database that aren't
  // certain enough to be valid.