code: def expanding_stdize(obj, **kwargs):
      
  
      return (obj - obj.expanding(**kwargs).mean()) / (
          obj.expanding(**kwargs).std()
      )
docs: Standardize a pandas object column-wise on expanding window.
  
      **kwargs -> passed to `obj.expanding`
  
      Example
      -------
      df = pd.DataFrame(np.random.randn(10, 3))
      print(expanding_stdize(df, min_periods=5))
               0        1        2
      0      NaN      NaN      NaN
      1      NaN      NaN      NaN
      2      NaN      NaN      NaN
      3      NaN      NaN      NaN
      4  0.67639 -1.03507  0.96610
      5  0.95008 -0.26067  0.27761
      6  1.67793 -0.50816  0.19293
      7  1.50364 -1.10035 -0.87859
      8 -0.64949  0.08028 -0.51354
      9  0.15280 -0.73283 -0.84907