code: def scale_sfs(s):
      
      k = np.arange(s.size)
      out = s * k
      return out
docs: Scale a site frequency spectrum.
  
      Parameters
      ----------
      s : array_like, int, shape (n_chromosomes,)
          Site frequency spectrum.
  
      Returns
      -------
      sfs_scaled : ndarray, int, shape (n_chromosomes,)
          Scaled site frequency spectrum.