val response = client.newCall(request)
	.execute()
 	.process<@FirstElementSet <SubResponse<Any>>,RestApiError.General>(moshi) { isSuccessful }
                        
fun <reified R, reified E : RestApiError> Response.process(
        moshi: Moshi,
        predicate: Response.() -> Boolean
): R {
    val annotation = `How to get the @FirstElement annotation on the argument 'R'`
    return if (predicate()) processResponse(typeInfo<R>(), moshi)
    else processError<E>(moshi)
}