Type error in line 151

[kashyap-adithya]

Hi Guys,
I am getting the following error
pointer_summarizer-master/data_util/data.py", line 149, in abstract2sents
while True:
TypeError: argument should be integer or bytes-like object, not 'str'

pointer_summarizer-master/data_util/data.py", line 151, in abstract2sents
start_p = abstract.index(SENTENCE_START, cur)
Any idea on how ti fix the error?