code: def start(self):
      # start the thread to read frames from the video stream
      t = Thread(target=self.update, name=self.name, args=())
      t.daemon = True
      t.start()
      return self
  
file_path: imutils/imutils/video/webcamvideostream.py
imports: from threading import Thread
  import cv2
label_desc: Use image node_id 2 for calling the WebcamVideoStream obj's underlying member method code with example usage: obj.start() and returns: self