visual studio 无法显示用graphviz绘制的决策图

from sklearn import tree
from sklearn.datasets import load_wine
from sklearn.model_selection import train_test_split
import graphviz
wine = load_wine()
Xtrain, Xtest, Ytrain, Ytest = train_test_split(wine.data,wine.target,test_size=0.3)
clf = tree.DecisionTreeClassifier(criterion="entropy")
clf = clf.fit(Xtrain, Ytrain)
score = clf.score(Xtest, Ytest) #返回预测的准确度
feature_name = ['酒精','苹果酸','灰','灰的碱性','镁','总酚','类黄酮','非黄烷类酚类','花青素','颜色强度','色调','od280/od315稀释葡萄酒','脯氨酸']
import graphviz
dot_data = tree.export_graphviz(clf
,out_file = None
,feature_names= feature_name
,class_names=["琴酒","雪莉","贝尔摩德"]
,filled=True
,rounded=True
)
graph = graphviz.Source(dot_data)
graph

最后运行结果是

<graphviz.files.Source object at 0x0000019AFA6CFD08>

按照教程应该是一个决策图啊，为什么不显示，试了半天没弄明白什么原因

最后一行代码用graph.view()就能显示了