convert chord maps back to tuples from list when loading tokenizer from a saved configuration

[shenranwang]

Hi,

I encountered an issue with chord maps when loading a saved tokenizer configuration from a file.

The CHORD_MAPS constant value has each chord map defined in a tuple, but after creating a tokenizer and saving the configuration, the chord maps are represented as lists (example snippet below):

...
"chord_maps": {
            "min": [
                0,
                3,
                7
            ],
            "maj": [
                0,
                4,
                7
            ],
...
            "9min": [
                0,
                4,
                7,
                10,
                13
            ]
        },
...

This is caused by json.dump converting all tuples into lists. This results in the detect_chords function always returning ukn chord tokens, i.e. 'Chord_A:ukn3', 'Chord_E:ukn3', etc.

There are a few ways to fix this:

• Make sure when saving the tokenizer config that the chord maps remain as tuples
• After loading the tokenizer, convert chord maps back into tuples
• Convert chord maps into lists and adjusting tests and documentation wherever necessary

I've implemented the second one for this PR, as it required the least amount of work and fixes the issue.

---

📚 Documentation preview 📚: https://miditok--141.org.readthedocs.build/en/141/

[Natooz]

Excellent, nice catch thank you!

I won't forget to also include chord maps in the save/load tests later!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (84de034) 91.23% compared to head (05732d8) 91.01%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
- Coverage   91.23%   91.01%   -0.23%     
==========================================
  Files          33       33              
  Lines        4917     4919       +2     
==========================================
- Hits         4486     4477       -9     
- Misses        431      442      +11     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.