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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 firmware command. Args: self (FirmwareCommand):
 the ``FirmwareCommand`` instance parser (argparse.ArgumentParser):
 parser to add the commands to Returns: ``None`` """

        group = parser.add_mutually_exclusive_group(required=True)
        group.add_argument('-d', '--downgrade', action='store_true',
                           help='downgrade the J-Link firmware')
        group.add_argument('-u', '--upgrade', action='store_true',
                           help='upgrade the J-Link firmware')
        return self.add_common_arguments(parser, False)