Should store serializable data to the app's sandbox, returning a unique identifier The returned UID has to be managed by the caller in order to retrieve the persisted data or to overwrite the contents using a successive storeCache: call. 
      Syntax
         
         
            - 
            (
            NSString *
            ) 
            
               storeSerializable
            
            : 
            (
            id< NSCoding >
            ) 
            serializable_in 
            
               withId
            
            : 
            (
            NSString *
            ) 
            uid_in
         
      
      Parameters
         
         
            - 
               serializable_in – 
               object adopting the NSCoding protocol to be persisted
            
- 
               id_in – 
               should be nil when storing an object adopting the NSCoding protocol for the first time, or an existing ID to overwrite previously stored content
            
Returns
         unique identifier (has to be managed by the caller in order to retrieve the persisted data)