python argparse autocompletion with file paths

So I have a python program that reads a config file like this:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('-c', '--config',  type=str, help='config file', required=True)

args = parser.parse_args()
cfg_filename = args.config

I want to be able to autocomplete paths in bash. For example, suppose the above program is called main.py and there is a config file called config_1.txt, structured as follows:

folder/
  main.py
  configs/
    config_1.txt

And suppose in my terminal it looks like

user@host:~/folder$ python main.py -c con

I hope pressing one tab gives:

user@host:~/folder$ python main.py -c config/

and then another tab gives

user@host:~/folder$ python main.py -c config/config_1.txt

I've tried adding

import argcomplete
argcomplete.autocomplete(parser)

but didn't work.