copy of a slice from a DataFrame

[metalray]

Hello Phyton Fans,
I just started a coursere training to learn more about phyton.
When I used the jupiter notebook provided by coursere the below code worked without error however
in my local anaconda environment the error says:

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A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: ....
 app.launch_new_instance()
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def answer_three():
        atleastonegold = df[(df['Gold.1']+df['Gold']) >1] #df.where(df['Gold']+df['Gold.1']>1)
        atleastonegold['summerminuswinter']= atleastonegold['Gold']-atleastonegold['Gold.1'] #=ADD a new column
        return atleastonegold #atleastonegold['biggestdifference'].idxmax()
answer_three()

I am only trying to create a new column.