code: func prepareExpiryEntriesForMissingData(mapByExpiringBlk map[uint64]*ExpiryData, missingKey *missingDataKey, btlPolicy pvtdatapolicy.BTLPolicy) error {
  	expiringBlk, err := btlPolicy.GetExpiringBlock(missingKey.ns, missingKey.coll, missingKey.blkNum)
  	if err != nil {
  		return err
  	}
  	if neverExpires(expiringBlk) {
  		return nil
  	}
  
  	expiryData := getOrCreateExpiryData(mapByExpiringBlk, expiringBlk)
  
  	expiryData.addMissingData(missingKey.ns, missingKey.coll)
  	return nil
  }
docs: // prepareExpiryDataForMissingData creates expiryData for missing pvt data