use callback for early stopping

tests/python_package_test/test_sklearn.py

@@ -166,9 +166,19 @@ def test_lambdarank_unbiased():
     q_train = np.loadtxt(str(rank_example_dir / 'rank.train.query'))
     q_test = np.loadtxt(str(rank_example_dir / 'rank.test.query'))
     gbm = lgb.LGBMRanker(n_estimators=50, lambdarank_unbiased=True, sigmoid=2)
-    gbm.fit(X_train, y_train, group=q_train, eval_set=[(X_test, y_test)],
-            eval_group=[q_test], eval_at=[1, 3], early_stopping_rounds=10, verbose=False,
-            callbacks=[lgb.reset_parameter(learning_rate=lambda x: max(0.01, 0.1 - 0.01 * x))])
+    gbm.fit(
+        X_train,
+        y_train,
+        group=q_train,
+        eval_set=[(X_test, y_test)],
+        eval_group=[q_test],
+        eval_at=[1, 3],
+        verbose=False,
+        callbacks=[
+            lgb.early_stopping(10),
+            lgb.reset_parameter(learning_rate=lambda x: max(0.01, 0.1 - 0.01 * x))
+        ]
+    )
     assert gbm.best_iteration_ <= 24
     assert gbm.best_score_['valid_0']['ndcg@1'] > 0.569
     assert gbm.best_score_['valid_0']['ndcg@3'] > 0.62