Set timer on detected object - object-detection

Question

i'm using yolo to detect object but i want to set timer for the detected object, can anyone help me?
so i want to make the object detecting with limited time for my projcet
i'm try my best but i don't have any idea how to do it
here is my code:
import cv2 as cv
import numpy as np
cap = cv.VideoCapture(0)
whT = 320
confThreshold = 0.1
nmsThreshold = 0.4
classesFile = "coco.names"
classNames = []
with open(classesFile, 'rt') as f:
classNames = [line.strip() for line in f.readlines()]
modelConfiguration = "yolov4.cfg"
modelWeights = "yolov4.weights"
net = cv.dnn.readNetFromDarknet(modelConfiguration, modelWeights)
net.setPreferableBackend(cv.dnn.DNN_BACKEND_OPENCV)
net.setPreferableTarget(cv.dnn.DNN_TARGET_CPU)
def findObjects(outputs,img):
hT, wT, cT = img.shape
bbox = []
classIds = []
confs = []
for output in outputs:
for det in output:
scores = det[5:]
classId = np.argmax(scores)
confidence = scores[classId]
if confidence > confThreshold:
w,h = int(det[2]*wT) , int(det[3]*hT)
x,y = int((det[0]*wT)-w/2) , int((det[1]*hT)-h/2)
bbox.append([x,y,w,h])
classIds.append(classId)
confs.append(float(confidence))
indices = cv.dnn.NMSBoxes(bbox, confs, confThreshold, nmsThreshold)
font = cv.FONT_HERSHEY_PLAIN
for i in indices:
label = str(classNames[classIds[i]])
x, y, w, h = bbox[i]
#print(x,y,w,h)
cv.rectangle(img, (x, y), (x+w,y+h), (255, 0 , 255), 2)
cv.putText(img, label, (x, y + 30), font, 3, (0,0,0), 3)
print("Jenis Mobil: " + label)
#cv.putText(img,f'{classNames[classIds[i]].upper()} {int(confs[i]*100)}%', (x, y-10), cv.FONT_HERSHEY_SIMPLEX, 0.6, (255, 0, 255), 2)
while True:
success, img = cap.read()
blob = cv.dnn.blobFromImage(img, 1 / 255, (whT, whT), [0, 0, 0], 1, crop=False)
net.setInput(blob)
layersNames = net.getLayerNames()
outputNames = [(layersNames[i - 1]) for i in net.getUnconnectedOutLayers()]
outputs = net.forward(outputNames)
findObjects(outputs,img)
cv.imshow('Image', img)
key = cv.waitKey(1)
if key == 27:
break
cap.release()
cv.destroyAllWindows()