How to push_back in objective-c std::deque @property?

I tried to push_back number to @property std::deque, but data doesn't add to deque and it empty

Code:

.h file

@interface HandTrackingViewController : CommonViewController

@property (readwrite, nonatomic) std::deque<double> vect;
@end

.mm file

#import "HandTrackingViewController.h"

@implementation HandTrackingViewController

- (void)mediapipeGraph:(MPPGraph*)graph
     didOutputPacket:(const ::mediapipe::Packet&)packet
          fromStream:(const std::string&)streamName {
    ...
    ...
    ...
    for (int handIndex = 0; handIndex < multiHandLandmarks.size(); ++handIndex) {
      ...
      for (int i = 0; i < landmarks.landmark_size(); ++i) {  
          self.vect.insert(self.vect.end(), {landmarks.landmark(i).x(), landmarks.landmark(i).y(), landmarks.landmark(i).z()});
      }
        for(int i=0; i < self.vect.size()-2; i+=3) {
            NSLog(@"(%f, %f, %f)", self.vect[i], self.vect[i+1], self.vect[i+2]); // deque is empty
        }        
    }
  }
}
@end

But if you make an intermediate deque and assign it to self.vect, then it works