public Optional<NormalBlockAdapter> getParent(final DataFetchingEnvironment environment) {
    final BlockchainQueries query = getBlockchainQueries(environment);
    final Hash parentHash = header.getParentHash();
    final Optional<BlockWithMetadata<TransactionWithMetadata, Hash>> block =
        query.blockByHash(parentHash);
    return block.map(NormalBlockAdapter::new);
  }
Returns the parent block of the current block.

@param environment the DataFetchingEnvironment
@return an Optional containing the parent block if it exists, otherwise an empty Optional
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/graphql/internal/pojoadapter/BlockAdapterBase.java