def _validate_cell_type(self, cell_type):
        """Validate cell_type is 'parent' or 'child'."""
        if cell_type not in ['parent', 'child']:
            msg = _("Cell type must be 'parent' or 'child'")
            raise exc.HTTPBadRequest(explanation=msg)
dataset/ETHPy150Open BU-NU-CLOUD-SP16/Trusted-Platform-Module-nova/nova/api/openstack/compute/legacy_v2/contrib/cells.py/Controller._validate_cell_type/original