I get an error and no output

Done! you provided a file with 1467844 data points.
Traceback (most recent call last):
File "P:\folder\Downloads\location-history-visualizer.py", line 255, in
main()
File "P:\folder\Downloads\location-history-visualizer.py", line 220, in main
oldest_timestamp, newest_timestamp = check_json_file(loc_hist)
File "P:\folder\Downloads\location-history-visualizer.py", line 39, in check_json_file
timestamps = [int(d['timestampMs']) for d in parsed_json]
File "P:\folder\Downloads\location-history-visualizer.py", line 39, in
timestamps = [int(d['timestampMs']) for d in parsed_json]
KeyError: 'timestampMs'