∀ {α : Type u_4} [inst : SizeOf α] (Has : Set α → Prop) (has_empty : Has ∅) (has_compl : ∀ {a : Set α}, Has a → Has aᶜ)
  (has_iUnion_nat : ∀ {f : ℕ → Set α}, Pairwise (Function.onFun Disjoint f) → (∀ (i : ℕ), Has (f i)) → Has (⋃ i, f i)),
  sizeOf { Has := Has, has_empty := has_empty, has_compl := has_compl, has_iUnion_nat := has_iUnion_nat } =
    1 + sizeOf has_empty