def METHOD_NAME(self, we, in_memory=False):
    if self.extension_function_kwargs_list is None:
        extension_function_kwargs_list = [dict()]
    else:
        extension_function_kwargs_list = self.extension_function_kwargs_list
    for ext_kwargs in extension_function_kwargs_list:
        # print(ext_kwargs)
        _ = self.extension_class.get_extension_function()(we, load_if_exists=False, **ext_kwargs)
        # reload as an extension from we
        assert self.extension_class.extension_name in we.get_available_extension_names()
        assert we.is_extension(self.extension_class.extension_name)
        ext = we.load_extension(self.extension_class.extension_name)
        assert isinstance(ext, self.extension_class)
        for ext_name in self.extension_data_names:
            assert ext_name in ext._extension_data
        if not in_memory:
            ext_loaded = self.extension_class.load(we.folder)
            for ext_name in self.extension_data_names:
                assert ext_name in ext_loaded._extension_data
        # test select units
        # print('test select units', we.format)
        if we.format == "binary":
            new_folder = cache_folder / f"{we.folder.stem}_{self.extension_class.extension_name}_selected"
            if new_folder.is_dir():
                shutil.rmtree(new_folder)
            we_new = we.select_units(
                unit_ids=we.sorting.unit_ids[::2],
                new_folder=cache_folder / f"{we.folder.stem}_{self.extension_class.extension_name}_selected",
            )
            # check that extension is present after select_units()
            assert self.extension_class.extension_name in we_new.get_available_extension_names()
        elif we.folder is None:
            # test select units in-memory and zarr
            we_new = we.select_units(unit_ids=we.sorting.unit_ids[::2])
            # check that extension is present after select_units()
            assert self.extension_class.extension_name in we_new.get_available_extension_names()
        else:
            print("select_units() not supported for Zarr")