case nil => exact λ _ => Ascending.nil
α : Type u
r : α → α → Prop
inst✝ : Trans r r r
β : Type v
r' : β → β → Prop
f : α → Option β
rel_pres : ∀ (a₁ a₂ : α), r a₁ a₂ → ∀ (b₁ b₂ : β), f a₁ = some b₁ → f a₂ = some b₂ → r' b₁ b₂
⊢ Ascending r [] → Ascending r' (filterMap f [])
no goals