∀ {α : Type u_1} {β : Type u_2} {p : α → Prop} {f : (a : α) → p a → β} {x : Option (Option α)}
  (H : ∀ (a : Option α), x = some a → ∀ (a_2 : α), a = some a_2 → p a_2),
  (Option.pmap (Option.pmap f) x H).join = Option.pmap f x.join ⋯