let f : ℂ → ℂ := λ z => z - u
case intro
U : Set ℂ
Q : Set ℂ → Set ℂ
ι : Type u_1
l : Filter ι
inst✝ : good_domain U
u : ℂ
hu : u ∈ Uᶜ
⊢ Set.Nonempty (𝓘 U)
case intro
U : Set ℂ
Q : Set ℂ → Set ℂ
ι : Type u_1
l : Filter ι
inst✝ : good_domain U
u : ℂ
hu : u ∈ Uᶜ
f : ℂ → ℂ := fun z => z - u
⊢ Set.Nonempty (𝓘 U)