fact: Definition subset_filter {T} (F : set_system T) (D : set T) := [set P : set {x | D x} | F [set x | forall Dx : D x, P (exist _ x Dx)]].
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed