proposition: Lemma fmapE {U V : Type} (f : U -> V) (F : set_system U) (P : set V) : fmap f F P = F (f @^-1` P).
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed