proposition: Lemma sle_filterL (p : pred A) ks x y : (x \notin ks) || p x -> x <=[ks] y -> x <=[filter p ks] y.
proof: Proof. by apply: index_filter_leL. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval order) pcm(options prelude ordtype seqext)