AttributeError: 'DataArray' object has no attribute 'flatten' in fractional_coverage notebook

[aarifsk]

running
result = frac_cov_cls.frac_coverage_classify(mosaic, clean_mask=clean_mask) raises an error, 'DataArray' object has no attribute 'flatten'
at ---> 55 mosaic_clean_mask = clean_mask.flatten()
in dc_fractional_coverage_classifier.py in frac_coverage_classify(dataset_in, clean_mask, no_data)

[dtip]

Your clean_mask needs to be a numpy array