@Override
  public Optional<BigInteger> getChainId() {
    if (protocolSchedule == null) {
      return Optional.empty();
    }
    return protocolSchedule.getChainId();
  }
Gets block header by hash

@param hash the block hash
@return the block header if block exists otherwise empty
app/src/main/java/org/hyperledger/besu/services/BlockchainServiceImpl.java