call the method parser.add_argument with string '--locale', string '-l', dest set to string 'locale', action set to string 'append',
parser . add_argument ( '--locale' , '-l' , dest = 'locale' , action = 'append' , default = [ ] , help = 'Locale(s) to process (e.g. de_AT). Default is to process all. ' 'Can be used multiple times.' )