code: def __init__(self, cfg, mode="eval"):
      self.cfg = cfg
      assert mode.lower() in [
          "test",
          "eval",
      ], "mode should be 'test' or 'eval'"
      self.mode = mode.lower()
      self.optimizer = None
  
      # build MOT data loader
      self.dataset = cfg["{}MOTDataset".format(self.mode.capitalize())]
  
      # build model
      self.model = create(cfg.architecture)
  
      if isinstance(self.model.detector, YOLOX):
          for k, m in self.model.named_sublayers():
              if isinstance(m, nn.BatchNorm2D):
                  m._epsilon = 1e-3  # for amp(fp16)
                  m._momentum = 0.97  # 0.03 in pytorch
  
      anno_file = self.dataset.get_anno()
      clsid2catid, catid2name = get_categories(
          self.cfg.metric, anno_file=anno_file
      )
      self.ids2names = []
      for k, v in catid2name.items():
          self.ids2names.append(v)
  
      self.status = {}
      self.start_epoch = 0
  
      # initial default callbacks
      self._init_callbacks()
  
      # initial default metrics
      self._init_metrics()
      self._reset_metrics()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import glob
  import re
  import paddle
  import paddle.nn
  import numpy
  from tqdm import tqdm
  from collections import defaultdict
  from ppdet.core.workspace import create
  from ppdet.utils.checkpoint import load_weight, load_pretrain_weight
  from ppdet.modeling.mot.utils import Detection, get_crops, scale_coords, clip_box
  from ppdet.modeling.mot.utils import MOTTimer, load_det_results, write_mot_results, save_vis_results
  from ppdet.modeling.mot.tracker import JDETracker, CenterTracker
  from ppdet.modeling.mot.tracker import DeepSORTTracker, OCSORTTracker, BOTSORTTracker
  from ppdet.modeling.architectures import YOLOX
  from ppdet.metrics import Metric, MOTMetric, KITTIMOTMetric, MCMOTMetric
  from ppdet.data.source.category import get_categories
  import ppdet.utils.stats
  from .callbacks import Callback, ComposeCallback
  from ppdet.utils.logger import setup_logger
label_desc: Use image node_id 1 to create a new Tracker object from inherited base classes: object with example: obj = Tracker(cfg, mode)