proposition: Lemma measurableD : setDI_closed (@measurable d T).
proof: Proof. move=> A B mA mB; case: (semi_measurableD A B) => // [D [Dfin Dl -> _]]. by apply: fin_bigcup_measurable. Qed.
imports: mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop ) reals ereal signed topology normedtype sequences esum numfun HB(structures)