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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 _norm(self, value):
 """Normalize the input value into the fundamental unit for this prefix type. :param number value: The input value to be normalized :raises ValueError: if the input value is not a type of real number """

        if isinstance(value, self.valid_types):
            self._byte_value = value * self._unit_value
            self._bit_value = self._byte_value * 8.0
        else:
            raise ValueError("Initialization value '%s' is of an invalid type: %s. "
                             "Must be one of %s" % (
                                 value,
                                 type(value),
                                 ", ".join(str(x) for x in self.valid_types)))