refine List.Nodup.length_le_of_subset ?_ ?_
α : Type u
β : Type v
inst✝¹ : BishopFin α
inst✝ : BishopFin β
f : α → β
f_inj : ∀ (a₁ a₂ : α), f a₁ = f a₂ → a₁ = a₂
⊢ List.length (List.map f (elems α)) ≤ List.length (elems β)
case refine_1
α : Type u
β : Type v
inst✝¹ : BishopFin α
inst✝ : BishopFin β
f : α → β
f_inj : ∀ (a₁ a₂ : α), f a₁ = f a₂ → a₁ = a₂
⊢ List.Nodup (List.map f (elems α))

case refine_2
α : Type u
β : Type v
inst✝¹ : BishopFin α
inst✝ : BishopFin β
f : α → β
f_inj : ∀ (a₁ a₂ : α), f a₁ = f a₂ → a₁ = a₂
⊢ List.map f (elems α) ⊆ elems β