from sklearn.ensemble import GradientBoostingClassifier
from sklearn.metrics import roc_auc_score

model = GradientBoostingClassifier()
model.fit(x_train, y_train)

train_auc = roc_auc_score(y_train, model.predict_proba(x_train)[:, 1])
print('Train AUC:', train_auc)  # High AUC indicates reduced bias

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