theorem instFiatSurfaceIsToParent
theorem instFiatSurfaceIsToParent: ∀ (x : Type) [FiatSurface.Is x], ContinuantFiatBoundary.Is x
theorem instFiatSurfaceIsToParent
theorem instFiatSurfaceIsToParent: ∀ (x : Type) [FiatSurface.Is x], ContinuantFiatBoundary.Is x