code: def joint_sfs_folded_scaled(ac1, ac2, n1=None, n2=None):
        # noqa
  
      # check inputs
      ac1, n1 = _check_ac_n(ac1, n1)
      ac2, n2 = _check_ac_n(ac2, n2)
  
      # compute site frequency spectrum
      s = joint_sfs_folded(ac1, ac2, n1=n1, n2=n2)
  
      # apply scaling
      s = scale_joint_sfs_folded(s, n1, n2)
  
      return s
docs: Compute the joint folded site frequency spectrum between two
      populations, scaled such that a constant value is expected across the
      spectrum for neutral variation, constant population size and unrelated
      populations.
  
      Parameters
      ----------
      ac1 : array_like, int, shape (n_variants, 2)
          Allele counts for the first population.
      ac2 : array_like, int, shape (n_variants, 2)
          Allele counts for the second population.
      n1, n2 : int, optional
          The total number of chromosomes called in each population.
  
      Returns
      -------
      joint_sfs_folded_scaled : ndarray, int, shape (n1//2 + 1, n2//2 + 1)
          Array where the (i, j)th element is the scaled frequency of variant
          sites with a minor allele count of i in the first population and j
          in the second population.