code: func createPurgeIndexByTxidRangeStartKey(txid string) []byte {
  	var startKey []byte
  	startKey = append(startKey, purgeIndexByTxidPrefix)
  	startKey = append(startKey, compositeKeySep)
  	startKey = append(startKey, []byte(txid)...)
  	startKey = append(startKey, compositeKeySep)
  	return startKey
  }
docs: // createPurgeIndexByTxidRangeStartKey returns a startKey to do a range query on index stored in transient store
  // using txid