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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 name_server_set(self, value):
 """Update named set of DNS name servers. :type value: str :param value: (Optional) new title :raises: ValueError for invalid value types. """

        if not isinstance(value, six.string_types) and value is not None:
            raise ValueError("Pass a string, or None")
        self._properties["nameServerSet"] = value