def test_empty_mapping(self):
        """
        Test with an empty mapping of children.
        """
        children: dict[str, xr.DataTree] = {}
        assert self.func(children) == (
            "<div style='display: inline-grid; grid-template-columns: 100%; grid-column: 1 / -1'>"
            "</div>"
        )

        Test with an empty mapping of children.
        
xarray/tests/test_formatting_html.py