subtitle translation issue for time code

when I try tu translate subtitle from EN to FR i get this (miss reading of time frame) :

EN:
[00:00:00.000 --> 00:00:02.000] [MUSIC PLAYING]
[00:00:02.000 --> 00:00:11.400] Got the guy that hey!

FR:
00:00:00,000 -- Cancer 00:00:02,000
[MUSIC PLAYING]
undefined
00:00:02,000 -- Cancer 00:00:11,400
Je l'ai eu !

I use :
libretranslate = os.getenv('LIBRETRANSLATE',"http://127.0.0.1:5000" )
lt = LibreTranslateAPI(libretranslate)
translate = lt.translate("{}".format(to_translate),"en","{}".format(targetlang))

Reproduce the issue with the shown LibreTranslateAPI call and the supplied EN-to-FR subtitle text. Inspect how subtitle time codes and surrounding text are passed through translation; done means timestamps remain intact and the output contains translated subtitle text without “Cancer” or “undefined”.

Written by the indexing model from the issue text.