def background_efficiency_score(y_true, y_pred, sample_weight=None):
    return efficiency_score(1 - y_true, 1 - y_pred, sample_weight=sample_weight)
BackgroundEfficiency == isBasB / isB == 1 - fpr
dataset/ETHPy150Open anaderi/lhcb_trigger_ml/hep_ml/metrics.py/background_efficiency_score