∀ {α : Type u_1} {β : Type u_2} {γ : Type u_3} [inst : AddCommGroup α] [inst_1 : UniformSpace α] [IsUniformAddGroup α]
  [CompleteSpace α] {f : β × γ → α}, Summable f → Summable fun b => ∑' (c : γ), f (b, c)