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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_arguments(self, parser):
 """Adds the arguments for the emulator command. Args: self (EmulatorCommand):
 the ``EmulatorCommand`` instance parser (argparse.ArgumentParser):
 parser to add the commands to Returns: ``None`` """

        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