faulty yolov8

from ultralytics import YOLO
import cv2

model = YOLO('yolov8n.pt')

video_path = 'traffic2.mp4'
cap = cv2.VideoCapture(video_path)

ret = True
while ret:
    ret, frame = cap.read()
    if ret:
        results = model.track(frame, persist=True)

        frame_ = results[0].plot()

        cv2.imshow('frame', frame_)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break