proposition: Lemma incl_subset {A : Type} (l1 l2 : seq A) : incl l1 l2 -> l1 \subset l2.
proof: Proof. intros Hi x; eapply Hi. Qed.
imports: mathcomp.ssreflect.ssreflect Classes.RelationClasses Classes.Morphisms List Tactics mathcomp(ssrfun ssrbool ssrnat seq)