TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType

[28YOGESH]

Traceback (most recent call last): File "api_for_multistep.py", line 110, in model_dump="model_saved/model_for_multi_step.ckpt" File "api_for_multistep.py", line 41, in init one_step = prepare_single_step_model(model_dump) File "/home/csn/Desktop/RetroExplainer/model/util.py", line 119, in prepare_single_step_model single_step_model = RetroAGT.load_from_checkpoint(ckpt, strict=False) File "/home/csn/anaconda3/envs/RetroExplainer/lib/python3.7/site-packages/pytorch_lightning/core/saving.py", line 169, in load_from_checkpoint model = cls._load_model_state(checkpoint, *args, **kwargs) File "/home/csn/anaconda3/envs/RetroExplainer/lib/python3.7/site-packages/pytorch_lightning/core/saving.py", line 205, in _load_model_state model = cls(*cls_args, **cls_kwargs) File "/home/csn/Desktop/RetroExplainer/model/RetroAGT.py", line 90, in init assert os.path.isfile(leaving_group_path) File "/home/csn/anaconda3/envs/RetroExplainer/lib/python3.7/genericpath.py", line 30, in isfile st = os.stat(path) TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType

Please sir give a solution for this error. How i can solve this error.