Use partial function (#7252)

Co-authored-by: Marek Petrovic <marek_petrovic@swissre.com>

Author: marekninja

xarray/backends/api.py

@@ -916,7 +916,7 @@ def open_mfdataset(
     >>> lon_bnds, lat_bnds = (-110, -105), (40, 45)
     >>> partial_func = partial(_preprocess, lon_bnds=lon_bnds, lat_bnds=lat_bnds)
     >>> ds = xr.open_mfdataset(
-    ...     "file_*.nc", concat_dim="time", preprocess=_preprocess
+    ...     "file_*.nc", concat_dim="time", preprocess=partial_func
     ... )  # doctest: +SKIP
 
     References