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