proposition: Lemma map_finer_subset A : A \in P -> A \subset map_finer A.
proof: Proof. rewrite /map_finer; case (boolP (A \in P)) => [H _ |//]. by case: (sig2W _) => /= B. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype partition