Restkit Post object with RootKeyPath and return object without RootKeyPath

gistfile1.txt

    RKObjectMapping* merchantSignupMapping = [RKObjectMapping mappingForClass:[WLMerchantSignup class]];
    [merchantSignupMapping mapKeyPathsToAttributes: 
     nil]; 
    [paymentProcessorObjectManager.mappingProvider addObjectMapping:merchantSignupMapping];
    //[paymentProcessorObjectManager.mappingProvider setMapping:merchantSignupMapping forKeyPath:@""];
    [paymentProcessorObjectManager.mappingProvider setSerializationMapping:[merchantSignupMapping inverseMapping] forClass:[WLMerchantSignup class]];
    [paymentProcessorObjectManager.router routeClass:[WLMerchantSignup class] toResourcePath:SERVER_WLMERCHANTSIGNUP];
    //[paymentProcessorObjectManager.mappingProvider registerObjectMapping:merchantSignupMapping withRootKeyPath:@"merchant"];



[[RKObjectManager sharedManager] postObject:merchant usingBlock:^(RKObjectLoader * loader) {
        loader.objectMapping = [appdelegate.paymentProcessorObjectManager.mappingProvider objectMappingForClass:[WLMerchantSignup class]];
        //loader.targetObject = nil;
        [loader.serializationMapping setRootKeyPath:@"merchant"];
        loader.delegate = self;
    }];