code: def slice_columns(x, using=None):
      
      if using is None:
          using = range(0, len(x[0]))
      return [x[:,s] for s in using]
docs: Slice a numpy array to make columns
  
      Parameters
      ----------
      x : ndarray
          A numpy array instance
      using : list of integer or slice instance or None, optional
          A list of index or slice instance
  
      Returns
      -------
      ndarray
          A list of numpy array columns sliced