做minist手写数字分类识别的时候遇到这个报错
这个是做交叉验证数据集切分的时候报的错
```python
skflods = StratifiedKFold(n_splits=3,random_state=None) #把数据集切分成3份
for train_index,test_index in skflods.split(X_train,y_train_5): #拿到train和test的index
clone_clf = clone(sgd_clf) # 克隆和之前参数一样的模型
X_train_folds = X_train[train_index]
y_train_folds= y_train_5[train_index]
X_test_folds=X_train[test_index]
y_test_folds=y_train_5[test_index]
clone_clf.fit(X_train_folds,y_train_folds)
y_pred = clone_clf.predict(X_test_folds)
n_correct = sum(y_pred == y_test_folds)
print(n_correct/len(y_pred))
```