Nano model training

hi there,
I am trying to train a "nano" model on custom dataset by using google Colab but I can't generate the train command because of "Exp" error.
note: I have checked the nano.py file and it is already updated
here is the message:
Traceback (most recent call last):
File "/content/YOLOX/yolox/exp/build.py", line 13, in get_exp_by_file
current_exp = importlib.import_module(os.path.basename(exp_file).split(".")[0])
File "/usr/lib/python3.7/importlib/init.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1006, in _gcd_import
File "", line 983, in _find_and_load
File "", line 965, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'nano'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "train.py", line 115, in
exp = get_exp(args.exp_file, args.name)
File "/content/YOLOX/yolox/exp/build.py", line 51, in get_exp
return get_exp_by_file(exp_file)
File "/content/YOLOX/yolox/exp/build.py", line 16, in get_exp_by_file
raise ImportError("{} doesn't contains class named 'Exp'".format(exp_file))
ImportError: nano.py doesn't contains class named 'Exp'

Start with yolox/exp/build.py and train.py to trace how the experiment file is imported and how the Exp class is checked; compare that path with the referenced nano.py file. Reproduce the command in the reported Google Colab setup, then verify that the nano experiment loads successfully and the training command can be generated.