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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 group_id(self, value):
 """The unsubscribe group to associate with this email. :param value: ID of an unsubscribe group :type value: GroupId, int, required """

        if isinstance(value, GroupId):
            self._group_id = value
        else:
            self._group_id = GroupId(value)