proposition: Lemma ring_semi_sigma_additive : sigma_sub_additive mu -> semi_sigma_additive Rmu.
proof: Proof. move=> mu_sub; apply: content_ring_sigma_additive. by apply: ring_sigma_sub_additive. 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)