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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 unassign_grade_system_from_gradebook(self, grade_system_id, gradebook_id):
 """Removes a ``GradeSystem`` from a ``Gradebook``. arg: grade_system_id (osid.id.Id):
 the ``Id`` of the ``GradeSystem`` arg: gradebook_id (osid.id.Id):
 the ``Id`` of the ``Gradebook`` raise: NotFound - ``grade_system_id`` or ``gradebook_id`` not found or ``grade_system_id`` not assigned to ``gradebook_id`` raise: NullArgument - ``grade_system_id`` or ``gradebook_id`` is ``null`` raise: OperationFailed - unable to complete request raise: PermissionDenied - authorization failure *compliance: mandatory -- This method must be implemented.* """

        # Implemented from template for
        # osid.resource.ResourceBinAssignmentSession.unassign_resource_from_bin
        mgr = self._get_provider_manager('GRADING', local=True)
        lookup_session = mgr.get_gradebook_lookup_session(proxy=self._proxy)
        lookup_session.get_gradebook(gradebook_id)  # to raise NotFound
        self._unassign_object_from_catalog(grade_system_id, gradebook_id)