CoreData: this class is not key value coding-compliant for the key @count. at

[mohsinbmwm3]

Why it is giving this error. Why it is trying to querry @"sum.count". These exception are convering all my console log.

Any idea what is the reason behind.

[error] CoreData: An observer of NSManagedObjectContextDidSaveNotification illegally threw an exception.  
Exception = [<_PFWeakReference 0x600000ad5b20> valueForUndefinedKey:]: this class is not key value coding-compliant for the key @count. at (
	0   CoreFoundation                      0x00000001189c78ab __exceptionPreprocess + 242
	1   libobjc.A.dylib                     0x000000010e860ba3 objc_exception_throw + 48
	2   CoreFoundation                      0x00000001189c751d -[NSException init] + 0
	3   Foundation                          0x00000001159efb3f -[NSObject(NSKeyValueCoding) valueForUndefinedKey:] + 225
	4   Foundation                          0x00000001159ee919 -[NSObject(NSKeyValueCoding) valueForKey:] + 307
	5   Foundation                          0x00000001159effea -[NSArray(NSKeyValueCoding) _sumForKeyPath:] + 193
	6   Foundation                          0x00000001159f0a72 -[NSArray(NSKeyValueCoding) valueForKeyPath:] + 369
	7   Fusion360-Staging                   0x0000000102d907bc RKSetOfManagedObjectIDsFromManagedObjectContextDidSaveNotification + 140
	8   Fusion360-Staging                   0x0000000102d90c2c -[RKManagedObjectContextChangeMergingObserver handleManagedObjectContextDidSaveNotification:] + 364
	9   CoreFoundation                      0x00000001188f864b __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 137
	10  CoreFoundation                      0x00000001188f8581 ___CFXRegistrationPost_block_invoke + 86
	11  CoreFoundation                      0x00000001188f7b60 _CFXRegistrationPost + 541
	12  CoreFoundation                      0x00000001188f7469 _CFXNotificationPost + 822
	13  Foundation                          0x0000000115a2a459 -[NSNotificationCenter postNotificationName:object:userInfo:] + 82
	14  CoreData                            0x000000010f72440f -[NSManagedObjectContext _postContextDidSaveNotificationWithUserInfo:] + 3298
	15  CoreData                            0x000000010f714d56 -[NSManagedObjectContext _didSaveChanges] + 3296
	16  CoreData                            0x000000010f713ad5 -[NSManagedObjectContext save:] + 5012
	17  Fusion360-Staging                   0x0000000102d8c094 __84-[RKManagedObjectRequestOperation saveContextToPersistentStore:failedContext:error:]_block_invoke + 100
	18  CoreData                            0x000000010f71f113 developerSubmittedBlockToNSManagedObjectContextPerform + 151
	19  libdispatch.dylib                   0x00000001153abf5b _dispatch_client_callout + 8
	20  libdispatch.dylib                   0x00000001153bdd72 _dispatch_lane_barrier_sync_invoke_and_complete + 132
	21  CoreData                            0x000000010f71f02c -[NSManagedObjectContext performBlockAndWait:] + 244
	22  Fusion360-Staging                   0x0000000102d8bd02 -[RKManagedObjectRequestOperation saveContextToPersistentStore:failedContext:error:] + 418
	23  Fusion360-Staging                   0x0000000102d8c310 -[RKManagedObjectRequestOperation saveContext:error:] + 400
	24  Fusion360-Staging                   0x0000000102d8cf07 -[RKManagedObjectRequestOperation saveContext:] + 663
	25  Fusion360-Staging                   0x0000000102d88f74 __79-[RKManagedObjectRequestOperation performMappingOnResponseWithCompletionBlock:]_block_invoke.342 + 1972
	26  Fusion360-Staging                   0x0000000102ddada3 -[RKResponseMapperOperation willFinish] + 899
	27  Fusion360-Staging                   0x0000000102ddbc18 -[RKResponseMapperOperation main] + 3560
	28  Foundation                          0x0000000115a414e9 __NSOPERATION_IS_INVOKING_MAIN__ + 17
	29  Foundation                          0x0000000115a3d728 -[NSOperation start] + 782
	30  Foundation                          0x0000000115a41e36 __NSOPERATIONQUEUE_IS_STARTING_AN_OPERATION__ + 17
	31  Foundation                          0x0000000115a41982 __NSOQSchedule_f + 182
	32  libdispatch.dylib                   0x00000001153bd767 _dispatch_block_async_invoke2 + 83
	33  libdispatch.dylib                   0x00000001153abf5b _dispatch_client_callout + 8
	34  libdispatch.dylib                   0x00000001153af164 _dispatch_continuation_pop + 836
	35  libdispatch.dylib                   0x00000001153adf27 _dispatch_async_redirect_invoke + 997
	36  libdispatch.dylib                   0x00000001153c0e77 _dispatch_root_queue_drain + 414
	37  libdispatch.dylib                   0x00000001153c1b17 _dispatch_worker_thread2 + 278
	38  libsystem_pthread.dylib             0x00000001154f8f8a _pthread_wqthread + 256
	39  libsystem_pthread.dylib             0x00000001154f7f57 start_wqthread + 15