code: func createCompositeKeyWithoutPrefixForTxid(txid string, uuid string, blockHeight uint64) []byte {
  	var compositeKey []byte
  	compositeKey = append(compositeKey, []byte(txid)...)
  	compositeKey = append(compositeKey, compositeKeySep)
  	compositeKey = append(compositeKey, []byte(uuid)...)
  	compositeKey = append(compositeKey, compositeKeySep)
  	compositeKey = append(compositeKey, util.EncodeOrderPreservingVarUint64(blockHeight)...)
  
  	return compositeKey
  }
docs: // createCompositeKeyWithoutPrefixForTxid creates a composite key of structure txid~uuid~blockHeight.