You can set arbitrary data in the transaction, for example a transaction ID. Docs here

Set a key:

@flow
def pipeline(filename: str, contents: str):
    with transaction() as txn:
        txn.set("filename", filename)
        write_file(filename, contents)

Consume it:

@write_file.on_rollback
def del_file(txn):
    "Deletes file."
    os.unlink(txn.get("filename"))