Error db.DBInvalidArgError unexpected file type or format

[iamvinny]

I'm trying to run the script but I keep getting the following error

➜  walletool git:(master) ✗ python3 wt_extract_keys.py -d "wallet_files/wallet.dat" -v 0
Traceback (most recent call last):
  File "/Users/vinny/Downloads/walletool/wt_extract_keys.py", line 31, in <module>
    main()
  File "/Users/vinny/Downloads/walletool/wt_extract_keys.py", line 19, in main
    w_data = read_wallet_dat(args.filename)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/vinny/Downloads/walletool/walletool/wallet_files.py", line 16, in read_wallet_dat
    d.open(filename, 'main', db.DB_BTREE, db.DB_THREAD | db.DB_RDONLY)
bsddb3.db.DBInvalidArgError: (22, 'Invalid argument -- __db_meta_setup: /Users/vinny/Downloads/walletool/wallet_files/wallet.dat: unexpected file type or format')