proposition: Lemma encoded_equivE : e' =2 [rel x y | e (ED x) (ED y)].
proof: Proof. by move=> x y; rewrite /encoded_equiv /= encModRelE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice) mathcomp(seq fintype)