Welcome, friend,
vtkInteractorStyleMultiTouchCameraExample doesn’t implement, override nor inherit any methods called EndGesture() or StartGesture() hence the error. Why such error is in that example left me scratching my head…
Anyway, I suggest replacing StartGesture() with OnStartRotate(). Likewise, EndGesture() with OnEndRotate(), if the swipe gesture is meant to rotate the model. The forementioned methods are both defined in vtkInteractorStyleMultiTouchCamera. See whether those work.