FairMOT KeyError: 'epoch'

When i run " !python demo.py mot --load_model ./lib/models/fairmot_dla34.pth --conf_thres 0.4 " I get this error

Fix size testing. training chunk_sizes: [6, 6] The output will be saved to /content/gdrive/My Drive/FairMOT/src/lib/../../exp/mot/default heads {'hm': 1, 'wh': 4, 'id': 128, 'reg': 2} 2020-12-15 05:00:40 [INFO]: Starting tracking... Lenth of the video: 1500 frames Creating model... Traceback (most recent call last): File "demo.py", line 43, in demo(opt) File "demo.py", line 32, in demo use_cuda=opt.gpus!=[-1]) File "/content/gdrive/My Drive/FairMOT/src/track.py", line 73, in eval_seq tracker = JDETracker(opt, frame_rate=frame_rate) File "/content/gdrive/My Drive/FairMOT/src/lib/tracker/multitracker.py", line 184, in init self.model = load_model(self.model, opt.load_model) File "/content/gdrive/My Drive/FairMOT/src/lib/models/model.py", line 38, in load_model print('loaded {}, epoch {}'.format(model_path, checkpoint['epoch'])) KeyError: 'epoch'