fact: Definition powerset_filter_from : set_system (set Y) := filter_from [set M | [/\ M `<=` F, (forall E1 E2, M E1 -> F E2 -> E2 `<=` E1 -> M E2) & M !=set0 ] ] id.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed