fact: Definition sub_additive := forall (A : set T) (F : nat -> set T) n, (forall k, `I_n k -> measurable (F k)) -> measurable A -> A `<=` \big[setU/set0]_(k < n) F k -> mu A <= \sum_(k < n) mu (F k).
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)