{α α₂ β : Type w} →
  {m : Type w → Type u_1} →
    {motive : Std.Iterators.Types.Flatten α α₂ β m → Sort u} →
      ((it₁ : Std.IterM m (Std.IterM m β)) → (it₂ : Option (Std.IterM m β)) → motive { it₁ := it₁, it₂ := it₂ }) →
        (t : Std.Iterators.Types.Flatten α α₂ β m) → motive t