Omit x, y coordinates, x & y bounds from conversion

[Huite]

X and Y coords aren't relevant; they're stored in the Ugrid topology.

In particular, the original bounds might be somewhat messy (e.g. the triangle stuff...). If a user want the coordinates, they can use https://deltares.github.io/xugrid/api/xugrid.UgridDatasetAccessor.assign_face_coords.html

Which are nice and consistent (i.e. counterclockwise, and without repeated vertices).

[veenstrajelmer]

Tested with:

import xarray as xr
import xugrid as xu

file_nc = r'P:\archivedprojects\11206304-futuremares-rawdata-preps\data\CMIP6_BC\CMCC-ESM2\uo_Omon_CMCC-ESM2_historical_r1i1p1f1_gn_199001-200912.nc'
ds = xr.open_mfdataset(file_nc, chunks={'time':1})

topology = {"mesh2d":{"x":'i',
                      "y":'j',
                      "x_bounds":'vertices_longitude',
                      "y_bounds":'vertices_latitude',
                      }
            }

uds = xu.UgridDataset.from_structured2d(ds, topology=topology)
print(uds.coords)
print(uds.data_vars)

assert set(uds.coords) == set(['longitude', 'latitude', 'lev', 'mesh2d_nFaces', 'time'])
assert set(uds.data_vars) == set(['lev_bnds', 'time_bnds', 'uo'])

This now results in the expected coords/data_vars (and also dims)