Convert Rekordbox 6 XML to RB5 XML so you can import it to Rekordbox version 5

rb6_xml_to_rb5_xml.py

#!/usr/local/bin/python3

import xml.etree.ElementTree as ET
import sys
import os.path

next_TrackID = 1901
old_new = {}

filename = sys.argv[1]
if not os.path.isfile(filename):
    print("No such file %s" % filename)
    sys.exit(1)

# XML init
rekordbox_xml = ET.parse(filename)
root = rekordbox_xml.getroot()

for track in root.findall("./COLLECTION/TRACK"):

    old_new[track.attrib['TrackID']] = str(next_TrackID)
    track.attrib['TrackID'] = str(next_TrackID)
    next_TrackID += 1

for track in root.findall("./PLAYLISTS//TRACK"):
    old_key = track.attrib['Key']
    track.attrib['Key'] = old_new[old_key]

with open(filename + '.rb5.xml', "wb") as f:
    f.write(ET.tostring(root))

Hi, when i run this command in phyton i get this error:

 line 10, in <module>
    filename = sys.argv[1]
               ~~~~~~~~^^^
IndexError: list index out of range

Not sure how to use this script other than just run it.
Please let me know how to make this work. Thanks!