Type error Problem of 'Series(data frame) to str'

I followed a code from Kaggle as in the picture.
It changed Series to str. However, when I tried in my notebook, there is TypeError: ‘str’ object is not callable. I don’t know what is the matter.

train_set.head(9)

text = train_set.Review
text

print(type(text))

text_combined = str(text)

>Solution :

From what you commented, you overwrote your str function with a variable containing The Capstone project has been getting delayed since JanDont expect yourself to complete the specialization.
Change the assignment to that variable to some other variable name, and restart your kaggle kernet.