订正 4.训练模型.md 代码中的缩进和括号配对问题

docs/4.训练模型.md

@@ -413,8 +413,8 @@ def plot_learning_curves(model, X, y):
         y_val_predict = model.predict(X_val)
         train_errors.append(mean_squared_error(y_train_predict, y_train[:m]))
         val_errors.append(mean_squared_error(y_val_predict, y_val))
-plt.plot(np.sqrt(train_errors), "r-+", linewidth=2, label="train")
-plt.plot(np.sqrt(val_errors), "b-", linewidth=3, label="val")
+    plt.plot(np.sqrt(train_errors), "r-+", linewidth=2, label="train")
+    plt.plot(np.sqrt(val_errors), "b-", linewidth=3, label="val")
 ```
 
 我们一起看一下简单线性回归模型的学习曲线（图 4-15）：
@@ -714,7 +714,7 @@ log_reg.fit(X, y)
 X_new = np.linspace(0, 3, 1000).reshape(-1, 1)
 y_proba = log_reg.predict_proba(X_new)
 plt.plot(X_new, y_proba[:, 1], "g-", label="Iris-Virginica")
-plt.plot(X_new, y_proba[:, 0], "b--", label="Not Iris-Virginica"
+plt.plot(X_new, y_proba[:, 0], "b--", label="Not Iris-Virginica")
 ```
 
 ![](../images/chapter_4/图4-23.PNG)