code: def _ppoints(n, a=0.5):
      
      a = 3 / 8 if n <= 10 else 0.5
      return (np.arange(n) + 1 - a) / (n + 1 - 2 * a)
docs: Ordinates For Probability Plotting.
  
      Numpy analogue or `R`'s `ppoints` function.
  
      Parameters
      ----------
      n : int
          Number of points generated
      a : float
          Offset fraction (typically between 0 and 1)
  
      Returns
      -------
      p : array
          Sequence of probabilities at which to evaluate the inverse
          distribution.