proposition: Lemma msetKUidC A B : A `|` (B `|` A) = B `|` A.
proof: Proof. by rewrite msetUCA msetUid. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap