docs: def get_signed_simplex_volumes(cells, pts):
      """Signed volume of a simplex in nD. Note that signing only makes sense for
      n-simplices in R^n.
      """
      n = pts.shape[1]
      assert cells.shape[1] == n + 1
  
      p = pts[cells]
      p = numpy.concatenate([p, numpy.ones(list(p.shape[:2]) + [1])], axis=-1)
      return numpy.linalg.det(p) / math.factorial(n)