proposition: Lemma openE : open = [set A : set T | A `<=` A^°].
proof: Proof. exact: openE_subproof. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed