proposition: Lemma in_fnd V (f : {fmap K -> V}) (k : K) (kf : k \in domf f) : f.[? k] = Some f.[kf].
proof: Proof. by rewrite Some_fnd. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)