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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 append_to_arg_count(self, data):
 """ Add digit to the input argument. :param data: the typed digit as string """

        assert data in '-0123456789'
        current = self._arg

        if data == '-':
            assert current is None or current == '-'
            result = data
        elif current is None:
            result = data
        else:
            result = "%s%s" % (current, data)

        self.input_processor.arg = result