unsupported operand type(s) for +=: 'NoneType' and 'int';请问这是什么原因呀

Traceback (most recent call last):
File "train.py", line 84, in
main(opt)
File "train.py", line 76, in main
trainer.train(callbacks, val)
File "/share/disk1/ml/code/efficientteacher-main/trainer/trainer.py", line 532, in train
self.train_in_epoch(callbacks)
File "/share/disk1/ml/code/efficientteacher-main/trainer/ssod_trainer.py", line 285, in train_in_epoch
self.train_without_unlabeled(callbacks)
File "/share/disk1/ml/code/efficientteacher-main/trainer/ssod_trainer.py", line 402, in train_without_unlabeled
self.update_optimizer(loss, ni)
File "/share/disk1/ml/code/efficientteacher-main/trainer/ssod_trainer.py", line 445, in update_optimizer
self.ema.update(self.model)
File "/share/disk1/ml/code/efficientteacher-main/utils/torch_utils.py", line 331, in update
self.updates += 1
TypeError: unsupported operand type(s) for +=: 'NoneType' and 'int'
Killing subprocess 60073
Traceback (most recent call last):
File "/root/anaconda3/envs/effictteacher/lib/python3.6/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/root/anaconda3/envs/effictteacher/lib/python3.6/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/root/anaconda3/envs/effictteacher/lib/python3.6/site-packages/torch/distributed/launch.py", line 340, in
main()
File "/root/anaconda3/envs/effictteacher/lib/python3.6/site-packages/torch/distributed/launch.py", line 326, in main
sigkill_handler(signal.SIGTERM, None) # not coming back
File "/root/anaconda3/envs/effictteacher/lib/python3.6/site-packages/torch/distributed/launch.py", line 301, in sigkill_handler
raise subprocess.CalledProcessError(returncode=last_return_code, cmd=cmd)
subprocess.CalledProcessError: Command '['/root/anaconda3/envs/effictteacher/bin/python', '-u', 'train.py', '--local_rank=0', '--cfg', 'configs/ssod/custom/yolov5l_custom_ssod.yaml']' returned non-zero exit status 1.