{α : Type w} →
  {m : Type w → Type w'} →
    {β : Type w} →
      {motive : Std.Iterators.Types.StepSizeIterator α m β → Sort u} →
        (t : Std.Iterators.Types.StepSizeIterator α m β) →
          ((nextIdx n : ℕ) → (inner : Std.IterM m β) → motive { nextIdx := nextIdx, n := n, inner := inner }) → motive t