Compiler Error use @synthesizeAssociation in @safecategory

[davidfuzju]

#import "NSHTTPURLResponse+YTNetworkMethods.h"

#import <objc/runtime.h>

@safecategory(NSHTTPURLResponse, YTNetworkMethods)

@synthesizeAssociation(NSHTTPURLResponse, responsePlainBody)

@end

I got this compiler Error

Property declared in category 'YTNetworkMethods' cannot be implemented in class implementation