Python「plot_tree」を使おうとしたら「AttributeError: module 」エラーが出た件

from sklearn import tree
tree.plot_tree()

from sklearn import tree

>>> from sklearn.datasets import load_iris
>>> from sklearn import tree
>>> iris = load_iris()
>>> clf = tree.DecisionTreeClassifier()
>>> clf = clf.fit(iris.data, iris.target)
>>> tree.plot_tree(clf.fit(iris.data, iris.target)) 

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'sklearn.tree' has no

$ conda list | grep scikit
scikit-image              0.13.0              np112py36_0  
scikit-learn              0.19.0              np112py36_0  

$conda update scikit-learn

$ conda list | grep scikit
scikit-image              0.13.0              np112py36_0  
scikit-learn              0.21.2           py36h27c97d8_0