How to draw rectangle in opencv around fire detected object from keras model

This code is for detecting fire using tensorflow keras model and I do not know how to draw rectangle around the fire detected object:

model = tf.keras.models.load_model('my_model\\InceptionV3.h5')
video = cv2.VideoCapture(0)
while True:
    _, frame = video.read()
    im = Image.fromarray(frame, 'RGB')
    im = im.resize((224, 224))
    img_array = image.img_to_array(im)
    img_array = np.expand_dims(img_array, axis=0) / 255
    probabilities = model.predict(img_array)[0]
    prediction = np.argmax(probabilities)
    # if prediction is 0, which means there is fire in the frame.
    if prediction == 0:
        img = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)
    print(probabilities[prediction])
    cv2.imshow("Capturing", frame)
    cv2.imshow("Capturing", img)
    if cv2.waitKey(1) & 0xff == ord('q'):
        break
video.release()
cv2.destroyAllWindows()