class_docstr: Load MOT dataset with MOT format from video stream.
  Args:
      video_stream (str): path or url of the video file, default ''.
      keep_ori_im (bool): whether to keep original image, default False.
          Set True when used during MOT model inference while saving
          images or video, or used in DeepSORT.
code: def __init__(self, video_stream=None, keep_ori_im=False, **kwargs):
      self.video_stream = video_stream
      self.keep_ori_im = keep_ori_im
      self._curr_iter = 0
      self.transform = None
      try:
          if video_stream == None:
              print(
                  "No video stream is specified, please check the --video_stream option."
              )
              raise FileNotFoundError("No video_stream is specified.")
          self.stream = cv2.VideoCapture(video_stream)
          if not self.stream.isOpened():
              raise Exception("Open video stream Error!")
      except Exception as e:
          print("Failed to read {}.".format(video_stream))
          raise e
  
      self.videoframeraw_dir = (
          os.path.splitext(os.path.basename(self.video_stream))[0]
          + "_raw"
      )
      if not os.path.exists(self.videoframeraw_dir):
          os.makedirs(self.videoframeraw_dir)
  
imports: import numbers
  import os
  import sys
  from collections import deque
  from collections.abc import Mapping
  import six
  from ppdet.core.workspace import register, serializable
  from ppdet.utils.logger import setup_logger
  from ppdet.data.reader import BaseDataLoader, Compose
  import cv2
  from imageio import imread, imwrite
  import numpy
  import paddle
  from paddle.framework import core
label_desc: Use image node_id 1 to create a new MOTVideoStream object  with example: obj = MOTVideoStream(video_stream, keep_ori_im)