code: func prepareExpiryEntriesForPresentData(mapByExpiringBlk map[uint64]*ExpiryData, dataKey *dataKey, btlPolicy pvtdatapolicy.BTLPolicy) error {
  	expiringBlk, err := btlPolicy.GetExpiringBlock(dataKey.ns, dataKey.coll, dataKey.blkNum)
  	if err != nil {
  		return err
  	}
  	if neverExpires(expiringBlk) {
  		return nil
  	}
  
  	expiryData := getOrCreateExpiryData(mapByExpiringBlk, expiringBlk)
  
  	expiryData.addPresentData(dataKey.ns, dataKey.coll, dataKey.txNum)
  	return nil
  }
docs: // prepareExpiryDataForPresentData creates expiryData for non-missing pvt data