Create customized xml for cv2.CascadeClassifier

Hello I am trying to build an OpenCV application for detecting all the cars in a video streaming. I am working in Windows10 and developed the following code:
import cv2
cap = cv2.VideoCapture( ‘videostreaming’)
car_cascade = cv2.CascadeClassifier( ‘cars.xml’)
I have the following question : how to create a cars.xml or xml file in cv2.CascadeClassifier for locating all the cars in my parking.

Please refer to this example cascade.
You can find much more examples in the internet.