proposition: Lemma msetUKC A B : (A `|` B) `&` A = A.
proof: Proof. by apply/msetP=> x; rewrite !msetE maxnK. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap