OptionalFileBinaryFunction
class OptionalFileBinaryFunction<A, OA : ObservableValue<A>, B, OB : ObservableValue<B>>(argA: OA, argB: OB, lambda: (A, B) -> File?) : BinaryFunction<File?, A, OA, B, OB> , ObservableOptionalFile
Boilerplate which avoids having to use generics.
Similar to FileBinaryFunction, but the value can also be null.