code: def start(self):
      print("Start video")
      if self.dirname == "":
          print("invalid filename!")
          return
  
      self.cap = cv2.VideoCapture(self.dirname)
      fps = self.cap.get(cv2.CAP_PROP_FPS)
      self.frame_count = self.cap.get(cv2.CAP_PROP_FRAME_COUNT)
      print(fps)
      self.t0 = time.time()
      print(self.t0)
      self.valid = False
      try:
          resp = self.cap.read()
          self.shape = resp[1].shape
          self.valid = True
      except:
          self.shape = None
  
file_path: heart-rate-measurement-camera/video.py
imports: import cv2
  import numpy
  import time
label_desc: Use image node_id 2 for calling the Video obj's underlying member method code with example usage: obj.start() without return types