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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_root_gradebook_ids(self):
 """Gets the root gradebook ``Ids`` in this hierarchy. return: (osid.id.IdList) - the root gradebook ``Ids`` raise: OperationFailed - unable to complete request raise: PermissionDenied - authorization failure *compliance: mandatory -- This method must be implemented.* """

        # Implemented from template for
        # osid.resource.BinHierarchySession.get_root_bin_ids
        if self._catalog_session is not None:
            return self._catalog_session.get_root_catalog_ids()
        return self._hierarchy_session.get_roots()