code: func dbFetchBlockHashByID(dbTx database.Tx, id uint32) (*chainhash.Hash, error) {
  	var serializedID [4]byte
  	byteOrder.PutUint32(serializedID[:], id)
  	return dbFetchBlockHashBySerializedID(dbTx, serializedID[:])
  }
docs: // dbFetchBlockHashByID uses an existing database transaction to retrieve the
  // hash for the provided block id from the index.