code: def add_arguments(self, parser):
          
          group = parser.add_mutually_exclusive_group(required=True)
          group.add_argument('-l', '--list', nargs='?',
                             type=str.lower, default='_',
                             choices=['usb', 'ip'],
                             help='list all the connected emulators')
          group.add_argument('-s', '--supported', nargs=1,
                             help='query whether a device is supported')
          group.add_argument('-t', '--test', action='store_true',
                             help='perform a self-test')
          return None
docs: Adds the arguments for the emulator command.
  
          Args:
            self (EmulatorCommand): the ``EmulatorCommand`` instance
            parser (argparse.ArgumentParser): parser to add the commands to
  
          Returns:
            ``None``