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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 get_objective_id(self):
 """Gets the ``Id`` of the related objective. return: (osid.id.Id) - the objective ``Id`` *compliance: mandatory -- This method must be implemented.* """

        # Implemented from template for osid.learning.Activity.get_objective_id
        if not bool(self._my_map['objectiveId']):
            raise errors.IllegalState('objective empty')
        return Id(self._my_map['objectiveId'])