Torch.load() error

when I use the function of torch.load(), get a error, as follow:

Traceback (most recent call last):
File “/home/xllv/proj/Demo/”, line 7, in
vocab = torch.load("/home/xllv/proj/Demo/vocab.test")
File “/home/xllv/bin/anaconda3/lib/python3.7/site-packages/torch/”, line 387, in load
return _load(f, map_location, pickle_module, **pickle_load_args)
File “/home/xllv/bin/anaconda3/lib/python3.7/site-packages/torch/”, line 564, in _load
magic_number = pickle_module.load(f, **pickle_load_args)
_pickle.UnpicklingError: unpickling stack underflow

my code just have one line as follow:

vocab = torch.load(“vocab.test”)