∀ {𝕜 : Type u_1} [inst : NontriviallyNormedField 𝕜] {E : Type u_2} [inst_1 : NormedAddCommGroup E]
  [inst_2 : NormedSpace 𝕜 E] {E' : Type u_3} [inst_3 : NormedAddCommGroup E'] [inst_4 : NormedSpace 𝕜 E'] {f : E → E'}
  {s : Set E} {x : E}
  {f' : TangentSpace (modelWithCornersSelf 𝕜 E) x →L[𝕜] TangentSpace (modelWithCornersSelf 𝕜 E') (f x)},
  HasMFDerivWithinAt (modelWithCornersSelf 𝕜 E) (modelWithCornersSelf 𝕜 E') f s x f' ↔ HasFDerivWithinAt f f' s x