∀ {α β : Type w} {m : Type w → Type w'} [inst : Std.Iterator α m β] {a : Std.IterM m β}
  {motive : (a_1 : Std.IterM m β) → a.IsPlausibleIndirectSuccessorOf a_1 → Prop},
  Std.IterM.IsPlausibleIndirectSuccessorOf.below ⋯