maximumBannerSizeLandscape method
Implementation
@override
Future<BannerSize> maximumBannerSizeLandscape() async {
  final String sizeRaw =
      await methodChannel.invokeMethod("maximumBannerSizeLandscape");
  return AATKitBanner.stringToBannerSizeMap[sizeRaw] ??
      (throw StateError("Unknown banner size returned by method: $sizeRaw"));
}