Error in build_data.py

Hi,
Thank you for the source codes. It is giving error while running the train_triad.py file, while calling train function.
Please suggest the required modification.
Thanks in advance.

 File "/Data/chanchal_1821cs11/entity-coref-master/src/build_data.py", line 563, in worker
    X[i].append(X_triad[i])
IndexError: list index out of range