Wrong estimated accuracy values for multiclass classification using CBPE

[nnansters]

Describe the bug
We have a dataset for a multiclass classification problem. When estimating accuracy using CBPE the results are different depending on the label values being used.

Replacing the string valued labels by integer values does yields different, correct results.

To Reproduce

ref = pd.read_parquet('image_satellite_reference_index.pq')
ana = pd.read_parquet('image_satellite_analysis_index.pq')

replacement = {'water': 0, 'desert': 1, 'green area': 2, 'clouds': 3}
ref.replace({'y_true': replacement, 'y_pred': replacement}, inplace=True)
ana.replace({'y_true': replacement, 'y_pred': replacement}, inplace=True)

est = nml.CBPE(
    timestamp_column_name='timestamp',
    chunk_period='D',
    metrics=['accuracy'],
    y_true='y_true',
    y_pred='y_pred',
    y_pred_proba={'water': 'pred_proba_0', 'desert': 'pred_proba_1', 'green area': 'pred_proba_2', 'clouds': 'pred_proba_3'},
    problem_type='classification_multiclass',
    thresholds={'accuracy': ConstantThreshold(lower=0.95, upper=1.0)}
).fit(ref)

res = est.estimate(ana)
res.plot().show()

This code will not fail but contain incorrect values for accuracy.

The correct results are given when replacing the labels in y_true and y_pred with integers:

ref = pd.read_parquet('image_satellite_reference_index.pq')
ana = pd.read_parquet('image_satellite_analysis_index.pq')

replacement = {'water': 0, 'desert': 1, 'green area': 2, 'clouds': 3}
ref.replace({'y_true': replacement, 'y_pred': replacement}, inplace=True)
ana.replace({'y_true': replacement, 'y_pred': replacement}, inplace=True)

est = nml.CBPE(
    timestamp_column_name='timestamp',
    chunk_period='D',
    metrics=['accuracy'],
    y_true='y_true',
    y_pred='y_pred',
    y_pred_proba={0: 'pred_proba_0', 1: 'pred_proba_1', 2: 'pred_proba_2', 3: 'pred_proba_3'},
    problem_type='classification_multiclass',
    thresholds={'accuracy': ConstantThreshold(lower=0.95, upper=1.0)}
).fit(ref)

res = est.estimate(ana)
res.plot().show()

Expected behavior
Running both snippets of code (with and without replacing label values) should yield the same results.