code: func dbFetchVersion(dbTx database.Tx, key []byte) uint32 {
  	serialized := dbTx.Metadata().Get(key)
  	if serialized == nil {
  		return 0
  	}
  
  	return byteOrder.Uint32(serialized[:])
  }
docs: // dbFetchVersion fetches an individual version with the given key from the
  // metadata bucket.  It is primarily used to track versions on entities such as
  // buckets.  It returns zero if the provided key does not exist.