public Optional<Hash> getBlockHashByNumber(final long number) {
    return blockchain.getBlockHashByNumber(number);
  }
Retrieves the header hash of the block at the given height in the canonical chain.

@param number The height of the block whose hash should be retrieved.
@return The hash of the block at the given height.
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/query/BlockchainQueries.java