∀ {𝕜 : Type u_1} [hnorm : NontriviallyNormedField 𝕜] [inst : CompleteSpace 𝕜] (E : Type u_2)
  [inst_1 : NormedAddCommGroup E] [inst_2 : NormedSpace 𝕜 E] [inst_3 : FiniteDimensional 𝕜 E] (x y : E →ₗ[𝕜] E),
  (↑LinearMap.toContinuousLinearMap).toFun (x + y) =
    (↑LinearMap.toContinuousLinearMap).toFun x + (↑LinearMap.toContinuousLinearMap).toFun y