def _check_open(self):

        if not self.isopen:
            raise ClosedFileError("the file object is closed")
Returns a flattened string of HTML attributes based on the
dataset/ETHPy150Open PyTables/PyTables/tables/file.py/File._check_open--crossover with--dataset/ETHPy150Open openstack/horizon/horizon/utils/html.py/HTMLElement.attr_string