有人能帮我弄清楚为什么我在网格搜索属性 cv_results_ 中得到 nan 值吗？

如何解决有人能帮我弄清楚为什么我在网格搜索属性 cv_results_ 中得到 nan 值吗？

from sklearn.model_selection import gridsearchcv
from sklearn.linear_model import SGDClassifier
params = {'alpha': [0.001,0.01,0.1,1,10,100,1000],'penalty': ['l1','l2']}
lgrg = SGDClassifier(class_weight='balanced',loss='log')
clf = 
gridsearchcv(estimator=lgrg,param_grid=params,scoring=recall_score,cv=5,return_train_score=True)
clf.fit(train_x,train_y)
y_pred = clf.predict(x_test)

print(pd.DataFrame(clf.cv_results_))

如果我打印，我会得到 nan 值

cv_results output in the form of dataframe