loadAd method
Implementation
Future<void> loadAd() async {
print("fsfp_tag: NativeAd.dart. loadAd.");
_channel!.setMethodCallHandler(adsCallbackHandler);
Map params = FreestarUtils.paramsFrom(placement, targetingParams);
params["template"] = template;
unawaited(_channel!.invokeMethod('loadNativeAd', params));
}