OptionalOrientationUnaryFunction
class OptionalOrientationUnaryFunction<A, OA : ObservableValue<A>>(argA: OA, lambda: (A) -> Orientation?) : UnaryFunction<Orientation?, A, OA> , ObservableOptionalOrientation
Boilerplate which avoids having to use generics.
Similar to OrientationUnaryFunction, but the value can also be null.