xarray backed by numpy not dask array error

[artttt]

if an xarray has been computed then the array inside it is a numpy array not a dask array.

CCOG doesnt handle this case. The first error is
AttributeError: 'numpy.ndarray' object has no attribute 'chunks'

Would be a nice feature to be able to accept this case as input.
Would also be nice to be able to accept a numpy array.