def ts_fit(series: TimeSeries, params: Mapping[str, Any], **kwargs):
            """
            'Fits' transform by returning `scale` and `translation` fixed params.
            """
            # Ensure `component_mask` not passed via `kwargs` if specified `mask_components=True`
            # when transform created
            mask_components = params["fixed"]["_mask_components"]
            if mask_components:
                assert "component_mask" not in kwargs
            # Ensure 'fitted' is not in `params`:
            assert "fitted" not in params
            scale, translation = (
                params["fixed"]["_scale"],
                params["fixed"]["_translation"],
            )
            return scale, translation

            'Fits' transform by returning `scale` and `translation` fixed params.
            
darts/tests/dataprocessing/transformers/test_fittable_data_transformer.py