请问老师，我执行时报下面的错误该如何处理？谢谢
#存入CSV
st.export_data(data=data, filename=code, type=‘price’)
print(data)

Traceback (most recent call last):
File “E:/study/pythontest/QuantitativeTrading/example/stock.py”, line 18, in
st.export_data(data=data, filename=code, type=‘price’)
File “E:\study\pythontest\QuantitativeTrading\data\stock.py”, line 48, in export_data
data.to_csv(file_root)
AttributeError: ‘NoneType’ object has no attribute ‘to_csv’