Remark identify_Acc_b:
  forall x,
  Acc (order uf.(m)) x -> repr uf x <> a -> Acc (order (M.set a b uf.(m))) x.Remark identify_Acc:
  forall x,
  Acc (order uf.(m)) x -> Acc (order (M.set a b uf.(m))) x.

Lemma identify_wf: well_founded (order (M.set a b uf.(m))).