>>> import numpy as np
>>> import xarray as xr
>>> da = xr.DataArray(np.zeros((2,3)), coords=[('unknown', [1, 2]), ('unknown', [0, 90, 180])])
>>> da
<xarray.DataArray (unknown: 3)>
array([[0., 0., 0.],
       [0., 0., 0.]])
Coordinates:
  * unknown  (unknown) int64 0 90 180
>>> da.dims
('unknown', 'unknown')
>>> da.coords
Coordinates:
  * unknown  (unknown) int64 0 90 180
>>> da.sel(unknown=90)
ValueError: conflicting sizes for dimension 'unknown': length 2 on <this-array> and length 3 on 'unknown'