def _validate_cell_name(self, cell_name):
        """Validate cell name is not empty and doesn't contain '!',
         '.' or '@'.
        """
        if not cell_name:
            msg = _("Cell name cannot be empty")
            raise exc.HTTPBadRequest(explanation=msg)
        if '!' in cell_name or cell_name in '.' or '@' in cell_name:
            msg = _("Cell name cannot contain '!', '.' or '@'")
            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_name/swapped operands of `in`