Calculate rolling average for all columns pandas

I have the below dataframe: df = pd.DataFrame({‘a’: [2.85,3.11,3.3,3.275,np.NaN,4.21], ‘b’: [3.65,3.825,3.475,np.NaN,4.10,2.73], ‘c’: [4.3,3.08,np.NaN,2.40, 3.33, 2.48]}, index=pd….