feat(measure_theory/borel_space): lemmas about `is_pi_system_Ioo` and `finite_spanning_sets_in` (#8434)
feat(measure_theory/borel_space): lemmas about `is_pi_system_Ioo` and `finite_spanning_sets_in` (#8434)









leanprover-community/mathlib,leanprover-community/mathlib