error when running filter

[shammmmmless]

Error infomation:
Traceback (most recent call last):
File "CoCo-Ex_overhead_filter.py", line 115, in
df = df[(df['LEN-DIFF-TOKEN'] != 'None') ]
File "/root/anaconda3/envs/cocoex/lib/python3.6/site-packages/pandas/core/frame.py", line 2906, in getitem
indexer = self.columns.get_loc(key)
File "/root/anaconda3/envs/cocoex/lib/python3.6/site-packages/pandas/core/indexes/base.py", line 2900, in get_loc
raise KeyError(key) from err
KeyError: 'LEN-DIFF-TOKEN'