Can't open the index file

[jiangyingru]

How to resolve this error：

Traceback (most recent call last):
File "pairsqc.py", line 371, in
cis_trans_ratio (args.pairs, outfilename=CIS_TRANS_OUT_FILE_PATH, cols = cols)
File "pairsqc.py", line 239, in cis_trans_ratio
tb=pypairix.open(pairs_file)
pypairix.PairixError: Can't open the index file.