def test_open_mfdataset_dataset_attr_by_coords(self) -> None:
        """
        Case when an attribute differs across the multiple files
        """
        with self.setup_files_and_datasets() as (files, [ds1, ds2]):
            # Give the files an inconsistent attribute
            for i, f in enumerate(files):
                ds = open_dataset(f).load()
                ds.attrs["test_dataset_attr"] = 10 + i
                ds.close()
                ds.to_netcdf(f)

            with xr.open_mfdataset(files, combine="nested", concat_dim="t") as ds:
                assert ds.test_dataset_attr == 10

        Case when an attribute differs across the multiple files
        
xarray/tests/test_backends.py