proposition: Lemma mD : semi_setD_closed measurable.
proof: Proof. move=> A B Am Bm; exists [set A `\` B]; split; rewrite ?bigcup_set1//. by move=> C ->; apply: measurableD. by move=> X Y -> ->. 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)