proposition: Lemma fixfsetK : F fixfset = fixfset.
proof: Proof. by rewrite /fixfset -[in RHS]fixsetK// fset_fsub// F_bound//= fset_sub_val. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)