{n : ℕ} →
  (motive : QuaternionGroup n → Sort u_1) →
    (x : QuaternionGroup n) →
      ((i : ZMod (2 * n)) → motive (QuaternionGroup.a i)) →
        ((i : ZMod (2 * n)) → motive (QuaternionGroup.xa i)) → motive x