ImportError: cannot import name 'six'

运行from mlxtend.classifier import StackingClassifier 出现ImportError: cannot import name 'six'
from mlxtend.classifier import StackingClassifier
运行结果及报错内容
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
-21-396e39bd93be> in <module>
----> 1 from mlxtend.classifier import StackingClassifier

D:\User\lib\site-packages\mlxtend\classifier\__init__.py in <module>
     12 from .ensemble_vote import EnsembleVoteClassifier
     13 from .stacking_classification import StackingClassifier
---> 14 from .stacking_cv_classification import StackingCVClassifier
     15 
     16 __all__ = ["Perceptron", "Adaline",

D:\User\lib\site-packages\mlxtend\classifier\stacking_cv_classification.py in <module>
     18 from sklearn.base import TransformerMixin
     19 from sklearn.base import clone
---> 20 from sklearn.externals import six
     21 from sklearn.model_selection._split import check_cv
     22 

ImportError: cannot import name 'six'
已经安装了six 但是不知道问题出在哪 版本的问题吗
怎么解决呢 感谢~

Sklearm好像对版本有要求