code: def _eval_seq_centertrack(
      self,
      dataloader,
      save_dir=None,
      show_image=False,
      frame_rate=30,
      draw_threshold=0,
  ):
      assert isinstance(self.model.tracker, CenterTracker)
      if save_dir:
          if not os.path.exists(save_dir):
              os.makedirs(save_dir)
      tracker = self.model.tracker
  
      timer = MOTTimer()
      frame_id = 0
      self.status["mode"] = "track"
      self.model.eval()
      results = defaultdict(list)  # only support single class now
  
      for step_id, data in enumerate(tqdm(dataloader)):
          self.status["step_id"] = step_id
          if step_id == 0:
              self.model.reset_tracking()
  
          # forward
          timer.tic()
          pred_ret = self.model(data)
  
          online_targets = tracker.update(pred_ret)
          online_tlwhs, online_scores, online_ids = [], [], []
          for t in online_targets:
              bbox = t["bbox"]
              tlwh = [
                  bbox[0],
                  bbox[1],
                  bbox[2] - bbox[0],
                  bbox[3] - bbox[1],
              ]
              tscore = float(t["score"])
              tid = int(t["tracking_id"])
              if tlwh[2] * tlwh[3] > 0:
                  online_tlwhs.append(tlwh)
                  online_ids.append(tid)
                  online_scores.append(tscore)
          timer.toc()
          # save results
          results[0].append(
              (frame_id + 1, online_tlwhs, online_scores, online_ids)
          )
          save_vis_results(
              data,
              frame_id,
              online_ids,
              online_tlwhs,
              online_scores,
              timer.average_time,
              show_image,
              save_dir,
              self.cfg.num_classes,
              self.ids2names,
          )
          frame_id += 1
      return results, frame_id, timer.average_time, timer.calls
  
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 9 for calling the Tracker obj's underlying member method code with example usage: obj._eval_seq_centertrack(dataloader, save_dir, show_image, frame_rate, draw_threshold) and returns: results,  frame_id,  timer,  timer