超级大单、大单、中单、小单指标官网示例报错及如何解决？
由huasan123创建，最终由small_q 被浏览 29 用户
根据精品课程《超级大单、大单、中单、小单指标？（https://bigquant.com/wiki/doc/zhibiao-FDtdQk5sWH）报错，请问如何解决：
AttributeError Traceback (most recent call last) <ipython-input-1-2e4394eb98da> in <module> 57 ) 58 ---> 59 m4 = M.factorlens_preservation.v2( 60 factors_info=m3.data, 61 factor_fields={
AttributeError: 'NoneType' object has no attribute 'read'
https://bigquant.com/experimentshare/237925e0fddc481ab838db10c9e4fc2f
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