`querying.getvar` doesn't accept `chunks='auto'` kwarg

[anton-seaice]

When I run :

cc.querying.getvar(
  '1deg_jra55_iaf_omip2_cycle6', 
  variable='sea_level', 
  session=session, 
  frequency='1 monthly', 
  start_time='2000-01', end_time='2001-12', 
  chunks='auto'
)

I get this error:

File /g/data/hh5/public/apps/miniconda3/envs/analysis3-23.07/lib/python3.10/site-packages/cosima_cookbook/querying.py:385, in getvar(expt, variable, session, ncfile, start_time, end_time, n, frequency, attrs, attrs_unique, return_dataset, **kwargs)
    383 chunks = xr_kwargs.get("chunks", None)
    384 if chunks is not None:
--> 385     missing_chunk_dims = set(chunks.keys()) - set(da.dims)
    386     if len(missing_chunk_dims) > 0:
    387         logging.warning(
    388             f"chunking along dimensions {missing_chunk_dims} is not possible. Available dimensions for chunking are {set(da.dims)}"
    389         )

AttributeError: 'str' object has no attribute 'keys'

However, chunks='auto' should be a valid key word argument to be passed to xr.open_mfdataset().

[anton-seaice]

Per https://github.com/COSIMA/cosima-recipes/pull/305, it may be better to remove all chunking done by the cookbook, and use the xarray defaults (which are good now)