code: func FwdDepKeysFromList(c context.Context, base *dm.Attempt_ID, list *dm.AttemptList) []*ds.Key {
  	keys := make(sort.StringSlice, 0, len(list.To))
  	amt := 0
  	for qst, nums := range list.To {
  		keys = append(keys, qst)
  		amt += len(nums.Nums)
  	}
  	keys.Sort()
  	ret := make([]*ds.Key, 0, amt)
  	for _, key := range keys {
  		for _, num := range list.To[key].Nums {
  			ret = append(ret, ds.MakeKey(c,
  				"Attempt", base.DMEncoded(),
  				"FwdDep", dm.NewAttemptID(key, num).DMEncoded()))
  		}
  	}
  	return ret
  }
docs: // FwdDepKeysFromList makes a list of datastore.Key's that correspond to all
  // of the FwdDeps expressed by the <base, list> pair.