Fitting twice creates duplicate data in the results object

[nikml]

Describe the bug
Fitting twice creates duplicate data in the results object

To Reproduce
Steps to reproduce the behavior:
In the latest version run the code:

import nannyml as nml
from IPython.display import display
import warnings
warnings.filterwarnings("ignore")
reference_df, analysis_df, analysis_targets_df = nml.load_synthetic_car_loan_dataset()
analysis_df = analysis_df.merge(analysis_targets_df, left_index=True, right_index=True)
calc = nml.PerformanceCalculator(
    y_pred_proba='y_pred_proba',
    y_pred='y_pred',
    y_true='repaid',
    timestamp_column_name='timestamp',
    problem_type='classification_binary',
    metrics=['roc_auc',],
    chunk_size=20000)
calc.fit(reference_df)
calc.fit(reference_df)
results = calc.calculate(analysis_df)
display(results.to_df())

Expected behavior
Only 1 set of reference results would be present.

Screenshots & scripts

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.