proposition: Lemma msetIidPr {A B} : reflect (A `&` B = B) (B `<=` A).
proof: Proof. by rewrite msetIC; apply: msetIidPl. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap