exposure method
Implementation
@override
Future<void> exposure(
String flagkey, ExperimentVariant? variant, String instanceName) async {
final properties = {'variant': variant?.value, 'flag_key': flagkey};
if (variant == null) {
properties.remove('variant');
}
final ampli = Amplitude.getInstance(instanceName: instanceName);
await ampli.logEvent("\$exposure", eventProperties: properties);
await ampli.uploadEvents();
}