/**
 * Maps "discriminator" value to the sub-class name, so that inheritance is supported.
 */
- (id)initWithDictionary:(NSDictionary *)dict error:(NSError *__autoreleasing *)err {
    NSString * discriminatedClassName = [dict valueForKey:@"aTypeString"];
    if(discriminatedClassName == nil ){
         return [super initWithDictionary:dict error:err];
    }
    Class class = NSClassFromString([@"OAI" stringByAppendingString:discriminatedClassName]);
    if(!class) {
        class = NSClassFromString([@"OAI" stringByAppendingString:[discriminatedClassName capitalizedString]]);
    }
    if([self class ] == class) {
        return [super initWithDictionary:dict error:err];
    }
    return [[class alloc] initWithDictionary:dict error: err];
}