loadAd method
Implementation
Future<void> loadAd({AdRequest? adRequest}) async {
final map = adRequest?._toMap() ?? {};
map['parameters'] = {
_pluginType: _flutter,
_pluginVersion: MobileAds.pluginVersion,
}..addAll(adRequest?.parameters ?? {});
_channel.invokeMethod('load', map);
_finalizer.attach(this, _channel, detach: this);
}