wangrenz

> I "think" the root cause of this particular issue, is not being able to access the `v`-component of a MULTI-FIELD message, so I "think" the issue is actually resolved...

@fcannini Yes， only one variable can be read. e.g ```python ds_u = xr.open_mfdataset(path_list, concat_dim='valid_time', combine='nested', engine='cfgrib', backend_kwargs={ 'filter_by_keys':{ 'cfVarName': 'u', 'typeOfLevel':'isobaricInhPa'},'indexpath':''}) ds_v = xr.open_mfdataset(path_list, concat_dim='valid_time', combine='nested', engine='cfgrib', backend_kwargs={ 'filter_by_keys':{ 'cfVarName':...