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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_assessment_part(self):
 """Gets the parent assessment. return: (osid.assessment.authoring.AssessmentPart) - the parent assessment part raise: IllegalState - ``has_parent_part()`` is ``false`` raise: OperationFailed - unable to complete request *compliance: mandatory -- This method must be implemented.* """

        if not self.has_parent_part():
            raise errors.IllegalState('no parent part')
        lookup_session = self._get_assessment_part_lookup_session()
        return lookup_session.get_assessment_part(self.get_assessment_part_id())