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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 raw(self, raw):
 """ Sets the raw of this RuntimeRawExtension. Raw is the underlying serialization of this object. :param raw: The raw of this RuntimeRawExtension. :type: str """

        if raw is None:
            raise ValueError("Invalid value for `raw`, must not be `None`")
        if raw is not None and not re.search('^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$', raw):
            raise ValueError("Invalid value for `raw`, must be a follow pattern or equal to `/^(?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?$/`")

        self._raw = raw