∀ {α : Type u_1} [inst : Preorder α] [inst_1 : LocallyFiniteOrder α] {a b c : α}
  [inst_2 : DecidablePred fun x => c ≤ x],
  a ≤ c → Multiset.filter (fun x => c ≤ x) (Multiset.Ico a b) = Multiset.Ico c b