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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 dehex_app(parser, cmd, args):
 # pragma: no cover """ hex decode a value. """


    parser.add_argument('value', help='the value to base64 decode, read from stdin if omitted', nargs='?')
    args = parser.parse_args(args)
    return dehex(pwnypack.main.string_value_or_stdin(args.value))