∀ {R : Type u_1} {B : Type u_3} {A : Type u_4} [inst : CommSemiring R] [inst_1 : Semiring A] [inst_2 : Semiring B]
  [inst_3 : Algebra R A] [inst_4 : Algebra R B] (fe : { fe // fe.2 * fe.2 = 0 ∧ ∀ (a : A), Commute fe.2 (fe.1 a) }),
  (DualNumber.lift fe) DualNumber.eps = (↑fe).2