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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_args(p):
 """ Update parser with tool specific arguments. This overwrites was is done in utils.uns_args. """

    # dictionary for adding arguments
    dadd_args = {
        '--opfile': {
            'default': '',
            'metavar': 'f',
            'type': str,
            'help': 'Specify a parameter file '
                    '(default: "sim/${exkey}_params.txt")'}}
    p = utils.add_args(p, dadd_args)
    return p