proposition: Lemma in_msetI A B a : (a \in A `&` B) = (a \in A) && (a \in B).
proof: Proof. by rewrite !in_mset msetE leq_min. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap