simp at hv
α : Type u_1
xs : Finset α
h : ∃ x, xs = {x}
y : Finset α
v : α
hv : getUnique xs h = v
⊢ v ∈ y ↔ xs ⊆ y
α : Type u_1
xs : Finset α
h : ∃ x, xs = {x}
y : Finset α
v : α
hv : xs = {v}
⊢ v ∈ y ↔ xs ⊆ y