public Optional<BlockHeader> getBlockHeaderByHash(final Hash hash) {
    return blockchain.getBlockHeader(hash);
  }
Given a block number, returns the associated block with metadata and a list of transaction
hashes rather than full transactions.

@param blockNumber The height of the target block's header.
@return The referenced block.
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/query/BlockchainQueries.java